[AndrewH]

While I have not yet read the following books in the series, I can say that Princess of Mars included in the omnibus posted by HarryT is beautifully formatted.

edit: I downloaded and glanced at the Mousecatcher version and it is beautifully formatted as well. The illustrations in the Mousecatcher version are in color and of good quality, while the illustrations in the version HarryT posted are monochrome scans. Whichever one you choose will be a pleasure to read.