These threads got mixed up.
If you want a book PUBLISHED by SAS, then Littel et al is the one to get. I recommended it when you asked about a SAS book. But it wouldn't be my first choice for a book on mixed models for longitudinal data.... for one thing, it covers things other than longitudinal data.t
If you want books that use a lot of SAS, there are two by Verbeke and Mollenberghs:
Linear mixed models for longitudinal data
Models for discrete longitudinal data.
these are published by Springer. They're very good (although the latter has some typos). But they are kind of mathematical. They are deeper but less broad than any of the three below:
The clearest introductions to longitudinal data are, I think
Singer and Willett: Applied Longitudinal Data Analysis (also covers survival analysis.... does NOT cover models for noncontinuous DV)
Hedeker and Gibbons: Longitudinal Data Analysis (nice for its comparison of a variety of ways to model longitudinal data, DOES include noncontinuous DV)
Fitzmaurice, Ware and Laird: Applied Longitudinal Analysis
Peter L. Flom, PhD
www DOT peterflom DOT com