[John Jarrold]

99% of the books submitted directly by authors are totally unpublishable, and many are turned down after fewer than ten pages have been read. I really can't give percenatges about middle and end, though.

Have a look at the 'How authors/books are chosen' thread and you'll get more idea of this.

Never, NEVER re-send a book to an agent or publisher unless they have specifically asked you to do so. I did that half-a-dozen times in fifteen years in publishing, and I've only done it a couple of times since I set up the agency. And over all that time I've been seeing about thirty books every week. In almost every case, once you've said no, that's it. The author must move on. If a publisher says 'The characters are good, but I didn't think the end worked', that doesn't mean you should rewrite the end and send it back. Only do that if the publisher or agent says: 'I want to see this again if you...'.