This is also a very good book, but not easy to get (but replicated in PDF's from Arm anyway)
I believe that book (ARM ARM Second Edition) is the last ARM ARM available as hard copy. I managed to get a used copy for a reasonable price before it became a "collector's item". It only covers through ARMv5, but that's good enough for the fixed-point instructions that most people need. ARMv6 adds a bunch of instructions which are good for DSP applications but I doubt a C compiler would generate them. Anyway, you can set the compiler options to generate whichever ARM architecture version you want.
The really nice thing about ARMv5 and ARM ARM Second Edition is that ARM instruction set formats were still easy to follow and are summarized in a few tables. ARMv7 instruction formats are a real PITA and the ARMv7-AR ARM doesn't even try to come up with a clean table for instruction formats. IMO, "R" hasn't stood for "RISC" in a long time. But it's still a great processor