The shelves are all in good condition; this bookcase appears to be fairly old, and as such, the shelves are made from real wood, not particleboard or MDF.
The back panel is particleboard, and has some minor amount of moisture damage/chipping at the bottom; you can fix it, or use it as-is.
I have used it for the last 4-5 years like this without issue; the only reason I'm selling it is because I custom built a new one myself from scratch that suits my needs better.