It’s not a book, but the best place to start for anything on Op Crusader is without doubt The Crusader Project:
I must declare a slight interest, as the site is run by my good friend Andreas Biermann (who some of you may remember as GermanBoy, the author of numerous scenarios for Combat Mission). Andreas is fluent in German, English, and Italian (his wife is Italian) and has done much primary-source archival research in all three languages. He also understands the context well, both from his friends who have done field research in Libya and from his extensive researches as a keen hobby warmer. His own military experience was as a national serviceman in the Luftwaffe during the Cold War. I believe that all this makes him the first historian to have a really sound grip on the experience of Crusader from the perspective of all three of the major participants.
All the best,