The big question, is whether it is worth £7 a month. I mean, yes, I have been spending more than £7 a month on books, and yes there are eleventy-trillion titles available, apparently, but will it actually save me money?
I think possibly not.
I think Kindle Unlimited is fine if you are happy to take pot-luck, but less so if you have specific books you want to read. I went through my Goodreads "want to read" list, and none of the books on it were available on Kindle Unlimited. Of the authors represented in my "want to read" list, there were a few featured in short stories and anthologies. I don't know how the authors are getting paid for their work in this format, but the fee must be fairly low if they are all keeping their powder dry.
Someone in one of my Goodreads book clubs recommended a few books to me, so I shall read those - they aren't in a genre I typically read - while I'm still on the free trial and then we shall see. But honestly, I'd rather read what I want to read, even if it does mean paying for it.