[fjtorres]

Look to the samples.
Most ebook stores let you download a free sample; typically, 10% of the book.
That should let you see for yourself what the formatting is like. Also the writing style.
Plenty of books go off the rails, plotwise, near the end, so you might still end up with a turkey but in general samples are representative of the book's quality.

You might also want to check the dates for the book, if available. A deep backlist title first published before the ebook era and released early in the current, Kindle age is more likely to have issues since most of those were scanned and OCR'ed to varying degrees of proofing.

Again, the free sample is your best protection.

Finally, if you're really worried, skim around the book right after your first download it.
Most good ebookstores will let you return an ebook for a short time after purchase.

Most recent release ebooks are generally clean and well-proofed and well-formatted whether tradpubbed or Indie. Its the minimum expected to play the game.

Bottom line: samples are your best friend.