There have been lots of interesting blog posts on top ten lists of books on Paul and Jesus. For a good summary, see Michael Pahl's Stuff of Earth. On Hypotyposeis, What Books to Buy for Biblical Scholarship, Stephen Carlson hits a very important note, on how the beginner should build properly, from Critical Editions of the Bible, to Background texts, to Lexica and Indices and so on. There are some useful thoughts here, and for a similar reason one should be wary of embarking in a university setting on a Jesus / Paul course before one has done an Introduction to Biblical Studies as a prerequisite. I'd add something further in relation especially to Historical Jesus studies. I used to teach a one-term course on Jesus to second and third year students, but I found that it was very difficult to do this when they did not already have the necessary skills, background, methodology in place. How can you explain the way the Jesus Seminar works without first explaining how one gets to what they call the "Q Gospel"? How can one assess their assessment of the Gospel of Thomas unless one has first spent time studying that text? Happily, I was able to rework the course so that it became a two-term course, with term one on the critical study of the Gospels (and related literature) and then term two on the Gospels.
For similar reasons, and here I am influenced also by a conversation I recently had with Ken Olson, if I were to put together a top 10 list on Historical Jesus books, the majority would probably be key books you need to read before you can assess the books that are specially focused on Jesus. Yes, I'd like to have books like E. P. Sanders's Jesus and Judaism in there, of course, but I'd also strongly recommend something like Sanders' and Davies's Studying the Synoptic Gospels to get students a grounding in the preliminary questions. I might even hazard a guess that some of the problems in contemporary Historical Jesus study derive from the fact that people jump into Historical Jesus study, as if it is a discipline in its own right, before spending time working through the Synopsis, for example.