Writing cover copy/blurb is one of the hardest types of writing for me, and I know many other authors feel the same. I ask myself "why?" often. It shouldn't be hard writing a short version of your book to give people a flavour of it, but it is. Because it's hard to pull out the best parts into a readable, enticing couple of paragraphs while you've got a whole novel in your head.... It's impossible to keep a whole book in your head anyway, let alone shrink it down into two paragraphs! I quickly discovered that my best efforts were the ones that I wrote before I'd written the whole book.. I guess because my mind wasn't weighted down with all the info, just the early hooks. The best advice I can give anyone starting out is to write the blurb early, and think of it as a sales pitch not a summary.
Anyone who is good with blurbs has my undying admiration. It's a real skill. When I first started being bought by publishers (a half life ago) part of the mess of excitement was because they were going to do the official cover copy for me... lol! Although sometimes when it came in there were inaccuracies, or it wasn't as good as I'd hoped it might be. On a couple of occasions I even decided my own dismal efforts were comparable .. lol! But that's another story wink emoticon
If an author has been publisher published for a while they sometimes get rights back on earlier works, and then you're able to publish the book again. That means going back to writing a new cover copy for a very old book -- which brings it's own barrel load of author-angst. Not only is the story buried deep in your writing memory, but the publisher blurb has now become lodged in your memory too, like a mental road block. The publisher's blurb belongs to them though, it's their copyrighted material. You can't use it again and you probably wouldn't want to, so you've got to go back to the drawing board.
If you're reading this because you thought I was going to wave a magic wand and tell you how to do it, I'm not, I can't. But I know a lady who can. smile emoticon