Wizard in Glass was IV, I think you meant V... Wolves of the Calla. I liked it better than Wizard, but not as good as the Waste Lands. Song of Susannah (VI) is good, but rather short. Apparently King made up for it in the final book, which clocks in at just under 900 pages, based on what I read in my Grant publications newsletter.
I have read it, and it was really good. Not the best of the bunch in my opinion, but good nontheless. You have to start it, knowing that a little ways in you're going to start reading another story within the story. Except you already know the main characters a little (Roland, Alain, Cuthbert, Susan)
For those of you collectors with disposable income, you might want to look at the below link. In addition to getting the Artist's signed edition of the Dark Tower VII, they're packaging up with a special edition of The Talisman/Black House autographed both by the artist and by co-author Peter Straub. A little pricy, but not as much as it will be when they sell out.😱