For me an atlas is all about the maps. The text can be got elsewhere in better books, although having said that, Morkot's text in the Penguin Greek atlas is excellent.
I've got Penguin atlases of Greece, Rome and Egypt, and they are all the same - well-meaning, but barely worth the money, because they are done too much on the cheap. I find there's a huge amount of stuff I've had to add to the maps and to the indexes. But unfortunately, I'd have to recommend these Penguins, because you've got no real alternative unless you can afford a Barrington.
However, you should look at Samuel Butler's Atlas of Ancient and Classical Geography. Everyman published it in 1907, but their 1933 and 1952 editions used entirely different maps. Amazon now (as from 2010) do a paperback reprint of the original edition (a disaster - see my review of it!), or you can find it on Gutenberg. It is to some extent Victorian or even Georgian guesswork (Butler died in 1839, but his son revised the maps), and you'll need a magnifying glass to read it, but still it is a minor treasure.