I just finished the outstanding book, All About Asset Allocation, by Richard Ferri. While I am well versed on the topic, I still learned quite a bit as Ferri goes went into detail on every facet of the practice. The only negative was that there seemed to be a lot of repetition, but given how important this topic is, a little repetition is a good thing. Ferri excelled in providing plenty of low-cost providers of index funds to be used in your asset allocation plan, but fell short of suggesting many ETFs as the selection at the time of publication was not as extensive as it is now, 2006 (first edition).
If you want a step-by-step manual on proper asset allocation, this is your guide. Each chapter guides you along as you build fund by fund until you have a portfolio of up to 12 different asset classes by the end of the book. There are plenty of examples on where the research originated from (Fama and French, Markowitz, and more) and makes for an enjoyable and quick read. His other books are just as helpful.