Hi..We just got our Garden landscaped...
 

and a few plants & new lawn etc but I know nothing about gardening. Can anyone recommend a good book to help me maintain our lovely new garden?

I'm assuming you're in the UK? If so "The Garden Expert" by Dr D.G. Hessayon is very straightforward - you can get it for only a couple of quid on Amazon. If you want something a bit more glossy, but still easy to use, "The Complete How to be a Gardener" by Alan Titchmarsh is good. Good luck!