(An earlier version of this post appeared as a comment on SF SIGNAL, where the question "How do you find good self-published ebooks?" was asked.)
I use my smartphone for reading ebooks, with apps for Nook and Kindle. I also use Overdrive to borrow ebooks from my local library. The smartphone screen is close enough to a paperback size that I don’t have trouble reading off it; other people find it difficult.
This is a habit I’ve only picked up in the last couple of years, but I find myself reading a lot more ebooks than hardcopy books nowadays.
Finding good self-published books: Sometimes a struggle. Easiest way is to keep an eye on experienced writers who are, more and more, bringing out their rights-reverted backlist as ebooks. (Walter Jon Williams, one of my favorite writers, has brought out most of his backlist as ebooks, including the non-sf nautical adventure novels from the start of his career.) You can catch up on a lot of older books this way, and the numbers are increasing.
Sorting thru new self-published works is a lot harder.
Ratings on Amazon and Goodreads are generally useless. Even the most awful books get mostly four or five stars. I think the psychology behind this is that giving three stars or less makes you a meanie, and people don’t want to be seen as a meanie.
Actual Amazon/Goodreads reviews are a little better, but not by much. Too many of the reviews fall into the same four-or-five-stars mental trap, and give gushing approval for writing that clearly doesn’t deserve it. I find it actually better to read the three-star reviews, when there are any; they tend to give a much more realistic idea what one can expect to find in a book.
There are a number of ongoing attempts to establish websites devoted to legitimate and intelligent reviews of self-published books, but none of them seem to have really gained a reputation or foothold yet.
My occasional column here, “The Brave Free Books”, reviews mostly-ebooks that I’ve gotten for free from author’s promotions, drawings, or other sources. I tend to follow a “toughlove” model of reviewing, so some books get high marks (Sam Torode's novel THE DIRTY PARTS OF THE BIBLE, for one example), while others… don’t (but get a lengthy explanation why their work was sub-par). Also, I’m a meanie.
Amazon’s “Look Inside”, and similar features elsewhere, is your biggest friend in the search for good self-published books. Being able to read a sample has saved me time and disappointment on multiple occasions.
Other things to look at are the covers and marketing blurbs. If a blurb is poorly written or boring, the book probably will be too. (This recent post dealt with the writing of blurbs, and why some failed and others succeeded in piquing my interest.)
A decently designed cover is a promising sign. If a writer is willing to take the time and effort to make the packaging presentable and professional, it may mean they also took the time and effort to make the book’s content worthwhile as well. (This doesn’t always prove true. One of the fantasy books I reviewed had a spectacularly good cover, but I was only able to read three chapters before giving up on the effort.)
Looking for good self-published works is a lot like looking thru a slushpile. Both follow a similar bell curve: On one end, there’s a fairly small (but memorable) amount of the extremely awful my-god-what-were-they-thinking flat out BAD books. Then there’s a big climb up a hill of Not-Ready-For-Prime-Time books, with clear problems in structure, plotting, characterization etc, books that needed a rethink or rewrite before they should have been published. Then the other half of that big hill, the As-Good-As books, works that are “competent”, that are “okay”, but that don’t have a distinctive voice, don’t do anything new or fresh, that are essentially imitative, and that in the end can best be categorized as “meh”. And finally the other small end of that bell curve, where the books are satisfying, well-crafted, and memorable.
It would be nice if sorting the wheat from the chaff involved less effort on my part, or if there were trustworthy sources to do a lot of that pre-sorting for me. But the self-publishing world is still pretty much in its Wild West, Gold Rush hullabaloo days, so all the above is pretty much how I'm stuck doing it for now. I expect changes in coming years, but I'm sure not going to place any bets on what form they'll take.