The first book is pretty much a much longer version of his 2009 article on this site. It is not useful if you’ve read the article imo.
As far as I know, he abandoned almost everything he introduced in the second book except for using “athletic” stuff like jumps and med. balls in your program.
If the jargon is confusing then I’d suggest you make a list and ask people who’ve run several 5/3/1 programs or use its ideas in some part of their programming.
But I strongly recommend that you don’t spend time looking for the books or trying to actually buy them.
The second book is really confusing to read iirc. Far more confusing than 5/3/1 Forever. 5/3/1 Forever attempts to be coherent- the second book seemed like Wendler taking a bunch of stuff he wrote online in various places and putting them into a book.