The content of the 2nd edition Planescape books themself is ecellent, so this review will be purely about how the reproduced books look, both in print and PDF.
In short, this is passable, but there are pretty annoying problems.
Most glaringly, print quality is very light. This makes some of the text very hard to read, given that Planescape books are filled with yellowish/brown extra text. Quotes from denizens of the planes, headers of each section... On some pages the ink gets so light that even the text that is supposed to be black turns blue/grey, and at those points the yellow extra text is almost invisible. Monstrous Supplement in particular has some bits that are very hard to read.
At times this unreadablity is due to print problems, but at others it's due to scans simply being too lightened. The pages really could use re-leveling to make the text clearer, and darks darker.
Lesser problem is the bleeds. Often the art is supposed to cover the whole page has white borders around it, not reaching the edges of the print area. Of course this preferrable to text going over the edge of the print space way into the bleed, but it makes the presentation seem sloppy at points.
Others have already mentioned the maps at the end of the book, with the way they're being done is that you get both zoomed out picture of front and back of each poster, and then several zoomed in pictures that make the details easier to see and text actually readable.
But personally I really don't see any more sensible way of handling them in this format, short of actually doing proper full-size prints of then. And at that point you might as well be asking for all the books in the box to be properly separated.
So how would I improve this release?
The first obvious thing to do would be to relevel black and white in every page. It might seem like large task, but would tremendously improve the readability.
To improve presentation, one would have to do some adjustment of the scans, both resizing them to uniformly fit the pages, are on same height (just by looking at page numbers you can see that there's signifigant shifting within each individual book included) and adjusting art elements so that they properly begin in the bleed area, so that there's no awkward white borders around the pages.
If all of these are solved, I'll gladly buy the book again. If that happens, please make Premium Print an option.
In hypothetical perfect world the package would have all of the five books seperated and the maps would be printed properly, but I doubt we'll ever get anything like that.
[2 of 5 Stars!]