The mono is a limited edition as far as I know. It also doesn't include all the albums, but only the mono albums. It's a purist's box set.

The mono recordings supposedly sound fuller, punchier and just "better" than the stereo mixes. Not because they're in mono, but because the stereo versions just weren't mixed as well and have, according to some, degraded some of the attributes of the original mono recordings.

If you want a complete collection in a one box, you need to get the stereo set. Or if you don't mind multiple items, you can get the mono box and then buy the others individually. I believe only the stereo albums will be available individually.