The best plant books I find for reference are the 'Expert Book range' by Dr D.G. Hessayon. The have a Flowering shrub expert, a bedding plant expert and various other plant related experts. I find them handy as they are not too big and you can just go to the expert you want e.g. bedding plants and look up your plant by either common or latin name. There is also advice on each plant but not enough to make it boring

And no I am not on commission

You can buy them in B&Q on Amazon or any good bookshop