[fjtorres]

Kindle Unlimited is not for everybody. (Like, duh.)
It might be for you if...
... you read a lot...
...owning is secondary to reading (its not for hoaders)...
...you aren't hung up on vetting or gatekept content...
...you are always looking for new authors to try...
...you aren't looking for specific, familiar books or authors...
...you read a whole lot..

Still there?
Still interested?
Okay, to understand Kindle Unlimited you need to keep in mind that it exists to serve both readers and authors.

For readers it is meant as a way to discover new good authors, risk-free.
New goes first.
You almost certainly will not find big name authors on KU. They don't need discovery; they have no shortage of fans. Amazon salts KU with a few dozen (hundreds?) of familiar titles here and there but KU is primarily a channel for small traditional publishers and Independent author-publishers, Indies in the US sense (not the UK usage).
This is because, for authors, KU is a marketing tool. A place where they have a chance to shine and find fans without having to deal with the shadow of the big names. It's a place for quirky, experimental stories, niche material, new voices, and old. A place where veteran authors can be more than midlist afterthoughts on a bottom shelf deep in the back of a dusty bookstore. There are almost no BPH titles. That is a feature not a bug.

If you walk into a bookstore and ignore the payola-infested front tables and head instead for the back shelves (or used to) then KU might be for you. A place you can pick a book from a new to you author to see how long they can keep you engaged, risk free. If they lose you half way, you just walk away, no big loss. If they manage to delight you, well, jackpot! A new favorite author.
KU is a grab bag. You roam around sample the wares and see how lucky you get. There's well over a million titles waiting for somebody with enough free reading time to take a chance...

Not for everybody.
But it does have some 2-4M subscribers finding good reads...