Sticky Situations

How would you handle a situation that can only be referred to as 'sticky?'  By that I mean, someone who wants to do a good turn for someone else, but it winds up leaving you in the muck.  Here's what I'm talking about:

Often I receive requests to read books by others, and generally, they're really pretty good.  But now and again, you're going to see a self-published author that JUST CAN'T WRITE.  I regularly haunt the bookstores (as I'm sure many of you do), and I have a friend who works at one of them.  Recently a local author came into her shop and wanted to know if she could sell copies of his book, which he had priced at $5 each.  It sounds like a reasonable price, in the beginning.  The books weren't really books, but only novellas; stopping at around 80 or 90 pages each. 

Here's where the problem begins: she told him I have a blog, and she'd ask if I would read the books and review them for him.  Since I've done this many times before, it didn't seem like a problem.  So I took them both home, and the same night I called and let him know I had them and would get to them in a couple of weeks because I had other books I had to finish first.  A couple of days later he called and asked if I had a chance to read any of them, and I told him no, I hadn't been able to get to them yet.

And then I read them.  And wished I hadn't.  One was a police procedural that had way too many errors, beginning on the first few pages.  Example:  A body is found fully clothed, but the attending detective tells everyone to "round up all the sex offenders."  Why?  If the body was fully clothed, and you hadn't even brought it to the morgue to check for sexual activity, why would you haul in all the sexual offenders?...and it went downhill after that...with error after error after error, and just plain bad writing.

So now I'm in the position of having to notify this person and tell him he needs to rewrite most of the book because it's just plain awful; and having to ask my friend if she read the book before she passed it on to me (guaranteed she didn't).  Don't get me wrong; if I read a book and it's terrible, I have no problem putting that on my blog.  You can't change bad writing, bad plot, or bad ideas no matter how hard you try.  I just hate the idea of dashing someone's aspirations, especially since it was self-published and he paid to publish it.  I'm going to put it as nicely as I can, and hope for the best, but I don't know how nicely you can say, 'you can't write.'

I'd be interested to hear how others have handled this situation, if you've ever had it happen.  If not, I'd still like to hear from you.