I have just finished reading Kaler "Stars and their Spectra" and believe it or not I found it better than the average textbook to read. Maybe I was a little more interested than in other subjects...
. Highly recommended.
I also found "Practical Amateur Spectroscopy" by Stephen Tonkin not too bad a read either, but I'd recommend reading Tonkin before Kaler.
There's a lot more detail in Kaler.
Another book I have is "Spectroscopy - The Key to the Stars" by Keith Robinson.
What Spectroscopy books do you have?
Al.