I would say the author is pretty clear about what he means. And unlike Darwin, he is actually basing his "evolution-is-degeneration" theory on real data:
4 - The fact that the information inside DNA is degenerating is a very much neglected aspect of life around us. This degeneration causes species, and also mankind, to degenerate and genes disappear instead of new ones with formerly unknown functions appearing.
LOSS OF GENES leads to new variation and new species
That the loss of a functional gene can lead to new variation is one aspect of biological change that is hardly realized. One single mutation can completely disable the a gene. With that the gene loses its function and causes a certain effect on the appearance of the individual carrying the gene. One clear example is albinism. The gene that produces the pigment has become dysfunctional. But it can also be more subtle: With many animals in the polar-regions, the gene that produces pigment in the skin has become dysfunctional. That's not the same as albinism, because albinism causes eyes to be red.
This photo of penguins shows how such a mutation can easily pop up in a certain population.
In the same way white lions (with black eyes) have been discovered in Africa. They will most likely quickly disappear in nature, because such a loss doesn't lead to good survival-prospects for lions.
White Lions: radical changes in appearance spontaneously originate in populations when a mutation disables a functional gene.
However, if such an elimination of a pigment gene takes place in an area with lots of snow, it can be an advantage, because the species is less visible and thus has a better chance to survive. The polar-bear, the dall-sheep and the snow-owl are good examples.
Besides the gene that is responsible for coat-coloring, the polar-bear also lost the genes that produce the core of the hairs. Therefor they are hollow and that is an advantage for them, because they isolate the bear very well against the cold. But it is a loss of functional genes that causes this advantage.
The process of domestication leads to new variations much more often, because these variations are wanted and therefore preserved. That's why our dogs, cats and rabbits are available in many different varieties. Those varieties are usually the result of genes that were eliminated completely or that sometimes still perform a minor part of their original function.
In that sense , the result of the loss of A, B, C, D and S-genes leads to respectively black, cinnamon-coloured, albino, blue-greyish and spotted mice. Loss of certain combinations of these genes eventually leads to mice that are chocolad-brownish, blue, silver-cinnamon-coloured, silver-roe-coloured, black spotted, cinnamon spotted and so on.
Breeding and selection can lead to a lot of new varieties (a lot of genes will be permanently eliminated or damaged and new combinations of active genes arise). But the possibility to breed continuously is limited, because eventually too many active genes will have been lost. So 'fresh blood' has to be brought in; original, functional genes have to be added. Species around the world become 'genetically poorer' as time goes by, no matter what kind of selection is used: natural or human.
Genetic Loss
In biology two interesting phenomenon's are wellknown: the 'bottleneck' and the 'founder-effect', that show us how genetic loss occurs. The bottleneck is an event where the genetic diversity of a certain population reduces significantly while being brought back to just a small number of individuals (later to return to its original size maybe). Many genes can be lost in the process, because these few individuals could never carry the genetic variety of the whole population.
The founder-effect is something similar and starts working when a certain number of individuals split from a mother-population, and establish their own population separately from this mother-population. When one male and one female arrive on a remote island for instance, they can create a new population. This population will only have the limited genetic variation that was already present within the original founders of this population.
On top of that there will be a certain amount of inbreeding. The advantage of inbreeding is that hidden (recessive) qualities can be made manifest, that leads to quick new variation which makes possible selection and adaptation.
On the other hand, inbreeding could lead to an increased chance of hereditary defects, thus to degeneration. In the founder-effect - which is the most common mechanism for species-formation (when individuals split from the main population and get reproductively isolated) - the appearance of new variation, gene-loss and degeneration are closely related.
Degeneration exists
Many examples of biological change in living nature, which are often used to prove evolution, are in fact examples of degeneration:
1 - Rudimentary (reduced) organs are still considered as strong proof in favor of evolution. But the reality shows us it is a loss, losing something, not the development of something that originally wasn't there. It's a form of degeneration.
2 - Human hereditary illnesses are often caused by a mutation of a gene that was originally good. From that moment on the flaw is passed on to other members of a family according to heriditary laws. In first instance, however, the gene was good. And most other people outside this family have the good gene. All kinds of isolated groups of people show to have their own specific hereditary illnesses. But we have to keep in mind it's a malfunction of something that originally functioned perfectly. It's not just another step on the evolutionary diary. So if we go back in time far enough (thousands of years), until we reach the time of our ancestors, we would find that they possess all the intact genetic information. It is not possible for them to have carried all our billions of genetic defects within their limited genepool.
3 - In isolated caves we can find various animal species that lost sight, like the blind water-scorpion in the caves of Moville, Romania, or the blind fish and lobsters in the longest cave-system on earth; Mammoth Cave, Kentucky, USA. These fishes, for example, have also lost the pigment in their bodies. They are completely pale. This cán be interpreted as 'an adaptation to the conditions', but nevertheless it is based on a loss of genetic information (for pigment and eyes).
A fish from the dark(!) Mammoth Caves with no eyes and no pigment.
Usually individuals with such mutations will not survive. But in dark caves it's no longer a disadvantage and they're still able to reproduce. Because of this reproduction, damaged genes spread and once a whole population lost the original genes, they will never return, because the information inside genes is too complex to originate from dysfunctional genes. It's like a genetic subroutine has gone lost.
4 - The non-flying cormorant lost the ability to fly. This species lives on an isolated island, with plenty of fish around, so diving from rocks is enough for this cormorant to stay alive.
The non-flying cormorant lost the ability to fly...
5 - Parthenogen lizards lost the ability to reproduce on a natural way, because the female-eggs have a double pair of chromosomes instead of a single pair. The lizards are exact copies of one another (clones) and they stimulate ovulation by simulating mating-behaviour among eachother. The masculine genetic information has gone lost through mutations, because this was no longer needed.
6 - One of the reasons the cheetah disappears is because of genetic loss and degeneration, like various researches have proven. By means of a 'bottleneck' all genetic information has gone lost and all cheetah's are lookalikes, like twins. In the supposedly 10.000 years this process has been going on, mutations did not lead to the needed variations; once something is lost, it will never return.
These examples and many more concerning this 'degeneration-law' leads us to this conclusion:
On the long run a species or population tends to lose genes and qualities which it doesn't necessarily need to survive.
Did the koala lose the genes that once helped him to have a more balanced diët?
Mutations occur randomly and one single mutation can be enough to disable a gene completely (just like a typing-mismatch will block computer-instructions). Therefor all the genes of a species have the risk to be eliminated sooner or later. Only if it strictly should not happen, because it decreases the chance of survival, the non-funtional gene will disappear.
In the long run it shows us that only the genes which are needed for survival in a specific environment, will last. Because of this a species might become completely dependent upon its environment, like, for example, the Koala, that only consumes very special eucalyptus-leaves. Eventually the genetic 'stretch' will have vanished, and if the environment changes again, a species could easily become extinct. It no longer has the genetic diversity to adapt to such changing circumstances.