It’s a beautiful day outside but seeing these covers for Fontana Modern Masters makes me want to stay in and design. From Wikipedia:

The Fontana Modern Masters were a series of pocket guides on the writers, philosophers, and other thinkers and theorists whose ideas were shaping the intellectual landscape of the twentieth century… The books were very popular with students who, according to Kermode, ‘bought them by the handful’ and were instantly recognisable by their eye-catching front covers, which featured brightly-coloured geometric designs overlaid with modern sans-serif typography.

These covers are the work of artists Oliver Bevan and James Lowe, and originally they could be combined and arranged to create new works of art. When Lowe replaced Bevan in 1975 the covers dropped the full bleed pattens in favor of white backgrounds but retained the shifting geometric shapes.