I second the recommendation for Andy B's book, it's very good. I also liked Anthony Louis' book, it's short but very intelligent and concise. From the German books, I liked Angelina Schulze's ideas about person cards (although the rest of her book is weak IMO).
I started many years ago with Anne Biwer's German book and base my Lenormand work still on her card meanings (available on the Internet at Amalthia).
Caitlin Matthews' book is very useful, too, although I'm not always in the same boat with her card meanings - but her chapters about reading techniques, cards and language and her exercises are excellent.
Rana George and Sylvie Steinbach - their card meanings too far removed from how I read (French school) but interesting ideas about HOW to read them in each of them. Steinbach's chapter about 5 card readings is very helpful and IMO the best in her book ;-)
I'm a cherrypicking reader and take from each book what I need. There are books I rely on for card meanings (like Biwer) who offer little else, and other books that explain the rest much better (card combinations, reading techniques like mirroring, knighting, counting..., how combinations work, how cards interact in a GT etc).
I have a Lenormand study journal where I build up the card meanings from books and my own readings, and I always write down from where I took each idea, combination, method, technique or nuance of meaning.
As first library, I'd go for Andy B, Rana George and Caitlin Matthews.