Brandon Wason has written up a helpful Historical Jesus Reading List, which he divides into the traditional periods,
• First Quest (Schweitzer, Talbert, Strauss, Wrede)
• No Quest (Kahler, Bultmann)
• New Quest (Kasemann, Bornkamm, Robinson)
• Third Quest (Vermes, Sanders, Crossan, Wright)
and includes a few other miscellaneous titles. They’re pretty good representative choices, though I agree with Michael Whitenton (in comments) that Schweitzer doesn’t belong in the first quest. His whole purpose was to kill it, and he really doesn’t fit into any period — like many geniuses, he’s a category unto himself. Doug Chaplin is also right that Meier is an essential listing under the third quest for the most comprehensive resource value, and I’d add Allison too. Chaplin (like Allison) takes issue with the periodisation of HJ scholarship, but I think “first”, “no”, “new”, and “third” remain roughly useful, so long as we remember that’s what they are — rough designations not for pigeon-holing scholars too seriously.
Chaplin (again in comments) also asks, that if we could read just one HJ book, what would it be? He chooses Sanders. I honestly couldn’t light on just one. I’d go with Schweitzer for lyrical prose (there are days I delight in reading Quest of the Historical Jesus just for the aesthetic writing), Meier for resource value (no project has been more thorough than A Marginal Jew), and Allison for nailing down Jesus as good as humanly possible (even here that’s cheating, because I have in mind his three-book “trilogy”, Millenarian Prophet, Resurrecting Jesus, and The Historical Christ, rather than one work). But if the question were rephrased to something like, “Which single book would I give to an outer-space alien who wanted to know about the historical Jesus?”, I suppose I’d hand over Allison’s Millenarian Prophet.