I bought a 1993 Yamaha DT200-R dirt bike and it obviously didn't come with a manual. I heard that Clymer books were detailed and I bought this one, since the WR250 is pretty similar to the DT200.
Except for my bike's gas tank capacity, oil tank capacity and minor modifications, this book described almost every screw and washer I could find. They take the bike down part by part, and put it back together. The book has hints and tips that save you alot of trouble and money. The first thing I did to my bike was maitenance, and the chapters are divided into intuitive sections. Of course, the easiest way of understanding is by diagrams, and the book is full of detailed sketches. The only problem I had, I think, was telling the difference between an oil fouled spark plug, and a carbon fouled plug. The pictures are in Black and White!!!
When I trade my bike in for a Honda 600, I think I'll by a Clymer book.