I bought the Lyman 48th and read the first several chapters with detailed info on powder, bullets, pressure, cases and case prep and detailed steps for both pistol and rifle loading. As well, it has specific chapters on bullet flight, casting and cleaning and a few other things I'm sure I've forgotten.
Then I read it all again.
With no mentor, it got me started in the right direction as far as equipment and it's use and sequence of use with safe practices.
The pistol, rifle and Contender data is fairly broad and makes for a good general reference across a variety of powder and bullet types, including cast.
Like ~Z says, there is no one best book that has everything you'll ever need or want to know. But I think the Lyman manual makes for a good starting point for learning equipment and process.