Diagnosing (not only) sourdough bread

Please, is there a good source (book/web) that would help better diagnose various bread defects? One with illustrative photos and more detailed explanation of what is a probable cause.

I often get pictures from my friends asking what thy did wrong. Sometimes it's clear, sometimes not. For example today:

This is a wheat-rye sourdough. 20% prefermented flour. It seems that the dough was a bit lazy to rise but my friend doesn't have much experience with poke testing. Baking was 15 minut 480°F / 250°C with steam (just a pot with hot water) + 40 min 350°F / 180°C.

Any idea for this photo and suggestion of a good book on this suject?

Thanks 

zdenka