Method of joining simple bookcase

[Jacob]

i would love to do everything in solid but it is just not practical, economical

Plenty of people use solid wood and find it practical and economical - from redwood through to exotics. It's a simple matter of choice.
I've used mdf (often found in skips) for bodging around the workshop but never for a client or item to sell. Confess to buying IKEA kitchen stuff too - feel guilty about that.

nor ethical.

er - quite the opposite, and a very big subject - too early in the day for me!

 

[Wood_womble]

Perhaps consider a laminated pine stair stringer for the shelves, much stiffer than MDF.

 

[Wood_womble]

Perhaps consider a laminated pine stair stringer for the shelves, much stiffer than MDF, supplied planed & sanded.