I loved those books. We had 2 in our school library -- huge, oversized volumns, as I remember. 7 wonders of the Ancient World and 7 Wonders of the New World, I think. I was about 11.
I read both books cover to cover in a month -- not being allowed to take them home. I was allowed use of the library only 1 hour per day and I would scramble in there fast (after orchestra practrice) to be first to get my hands on the books. I still vividly remember him swimming through the locks of the Panama Canal and diving down a well where the Mayans sacrificed young maidens.
Later I discovered a third volumn in the public library, but I didn't like it as much. I was very disappointed to learn that he had died in a sailing accident. I've known only one other person in my whole life who has read those books.
I remember the event well..... I finished the last page of both volumes.... I read all the words in both of those BIG books. I think I was 10 or 11.
I 've read them several times and for my 20th birthday in 1961 my mom gave me both volumes the Occident volume 1 and The Orient Vol II combined into a single book.
Since then I found most of his other books in used book stores,
The Book of Marvels is a standard reference and I check it whenever I need to refresh my memory on one of the places.