REEL ART was, for me, the book that opened the door to all those great 30's & 40's posters. Today, Heritage's catalogs serve the same function. That huge ART OF JAMES BOND poster book is THE book to have on OO7 posters, along with Thomas Nixdorf's tome. As much as I want to like it, Frangioni's Clint Eastwood book is only ok, because for me it commits the cardinal sin of spreading 1/2 or 3/4 of a poster across 2 pages which ruins the flow of the poster and frankly looks awful. And it's done throughout the book.
I don't know if this has been mentioned yet, but there is also the Japanese Viva OO7 book. It's a thin softcover book but it's packed with rare Japanese posters, chirashi's, handbills and all kinds of Bond goodness. The back section of the book has all the Man From UNCLE posters released in Japan.