I have the Hornady, Lee and Lyman manuals, latest editions. Between them I can usually find what I need, which is a starting load for a powder I have and a cartridge I need data for. When doing the research I pay attention to the listed max loads too - because the manuals don't always agree.
My longtime reloading friends all seem to have accumulated at least half a dozen manuals, some of them going back a ways. They keep manuals from reloading outfits (e.g. Lee, Lyman), powder companies (e.g. Alliant, Hodgdon), and bullet makers (e.g. Hornady, Nosler, Sierra, Speer). Part of the pleasure in reloading is the preliminary research.