You can get a preview of Packt books over on Safari [0].

Personally, I've found the quality of content and editing in Packt books to be consistently terrible. I won't click on a Packt book in my all you can read Safari Library subscription, I certainly wouldn't pay $5 for any of them.

At the opposite end of the spectrum, I can't recommend No Starch Press [1][2] enough.

0: http://my.safaribooksonline.com/browse?publisher=83&publishe...

1: http://shop.oreilly.com/category/publishers/no-starch-press....

2: http://my.safaribooksonline.com/browse?publisher=59&publishe...