“Gish is a creationist. You can’t expect him to tell the truth about the theory of evolution, can you?”
If your first priority is to protect a worldview based on either Darwinism or atheistic naturalism, do not read Gish’s book. Don’t go anywhere near anything written by Michael J. Behe, either, and you must completely ignore the major arguments presented by both Gish and Behe.
Sarcastic tone aside—I would say with great enthusiasm yes, look with careful focus into the writings and thinking of these men, as well as that of any serious scientists and philosophers you encounter along the way.
If you find yourself criticizing them based on labels alone or defaming their character, I would suggest you take note of this tactic.
I have read quite a bit of creationist literature, and studied a number of creationist websites.
When it comes to science they are either willfully self-deluded or they are lying.
They make the most outrageous claims about science, things that are documented to be incorrect, and when corrected they continue to make those same claims.
The reason for this is that they are not doing science; they are promoting their particular religious views. They are not bound by the rules of science, nor by evidence. This leads to repetition of the same falsehoods over and over.
Some of these claims have been seen, and refuted, so often that they have been numbered for easier reference. See Index to Creationist Claims by Mark Isaak.