Don't know a textbook; I would like to have one myself.
Call NCMA (National Concrete Masonry Association) and ask for the Concrete Masonry Manual and TEK Manual. They usually allow one copy per office depending on the size of the office. The TEK Manual has some great design information in it. They don't update the TEK sheets anymore so you have to go online to find the updates...they are free.
A copy of ACI 530 code/specification and commentary is good since it gives you the code, specifications and a practical commentary liked together.
A great publication and absolute must is the Masonry Designers Guide (published by The Masonry Society - TMS in Boulder, CO).
Both are probably available through ACI or TMS.
I think the timing of the 600+ page Masonry Designers Guide may lag behind the latest ACI 530 and IBC by one version, but the differences are very minor. the "meat" is the real value.
If you take one of the good seminars put on by ACI or a local masonry association, you may get a good package price on the books. The guide may also be available of CD.
Jim Amrhein's book is great because it is practical and covers the concepts well.
For LRFD design, "Engineered Masonry Design" by Glanville, Hatzinikolas and Ben-Omran is one of the best. It's based on Canadian Codes, but the methodology used is universal.