Joseph Kerman: The Beethoven Quartets
I bought this book primarily to gain some insight into Beethoven's Gross Fugue and the opening fugue of the C# Minor quartet, which I plan to analyze here (I already have it transcribed into Encore).
However, I did enjoy the entire book, as it does highlight many aspects of Beethoven's evolution in this idiom for his entire career. There are enough musical examples, but the analysis is not as technical and detailed as I do them, but Kerman was a musicologist, not a composer-theorist. I highly recommend it, and after this read, I plan to get my Complete Beethoven Quartets book out and follow along to gain more detailed insights. I have some great recordings of the late quartets - my main interest - so this should be both illuminating and fun.