Hi, likewise have 2 girls 15 & 12 yrs - older one likes the Twiglight books and the Girl Missing series - anything by Sophie McKenzie, they both love Michael Morpurgo and the younger one likes the way David Walliams writes too.
Go to your local waterstones, sit in the coffee shop and let them browse the shelves for ages, reading the blurb is a good way to get the feel of the story.
Our local library has reduced its stock and the books on offer are limited.
A good book store should happily let the girls trawl the shelves, mine are often found sat on the floor going through the books.
Goodnight Mr Tom is also a lovely story to read for all ages!