Book Shelving Advice

I have tried many budget shelving units and kits that turned out to be 'budget' quality.
Heavy duty kits are expensive and not too nice looking for an office.

Any advice on materials, methods for shelving that will withstand a good number of computer reference books without looking as if it's going to snap in the middle...

I have about 40 books (heavy) ready for shelving on a masonry wall. Going with the DIY as a cheaper alternative. I may consider metal, but I'd much prefer wood.

we really need a rough size and rough budget to work it out

scaffold boards [old or new ]are ideal 2x1"baton on each end [assuming an alcove] or wall one end and 4x 4" screws through a board into the end

scaffold are 9"wide about £1-1.50p a foot
and will be ok unsupported for around 7 ft

A floor standing shelf unit made from 18mm mdf can be made to size and with upright dividers, support any weight of books.