There are so many books, articles and blog posts about the topic. And it's not the easy way to chose the right one, laconic and simple, with pragmatic advices and some real case studies.
The biggest issues for almost every "agile" related book is their size, about 300 pages (in general). But what about brief, all-sufficient book?
I can suggest two, short enough, books: Scrum and XP from the Trenches and Kanban and Scrum - making the most of both. The names of the books are self-explained.
You've got the "big picture" after the reading of these books.