There are good businesses with good books and there are good businesses with bad books and there are bad businesses with good books and bad businesses with bad books. You get the idea....
Just because a business has bad books.... it doesn't make it a bad business. Some business owners are not keeping good records because it helps them "obscure" their profits and lower their taxes.
I've seen very good businesses sell for prices below what they should have because the poor records made profits difficult to quantify.
If you take the time to unscramble the books you will often find a good business. Remember if the books are bad enough that the seller doesn't know how much profit he's making that might be an opportunity for a buyer, if you can sort out the books.