Really lovely teenage books sos help

Stargirl by Jerry Spinelli

When I was a teenager I enjoyed Jean Plaidy L M Montgomery, and the Jalna books by Mazo de La Roche. Don't know if they would appeal as much to teenagers these days.

I'm sorry she's ill, and hope she recovers soon.
Whenever I'm I'll, I re-read old favourites often things like Malory Towers and The Chalet School, or PG Wodehouse.

I recommend the Tiffany Aching series by Terry Pratchett, it begins with the Wee Free Men. Very funny, gripping, and moving, but not too moving IYSWIM.
She might like Hitchhiker's Guide to the Galaxy too.

Yes that magazine is fantastic. I get it for my teens.

There's a lovely magazine called teen breathe that's all about mindfulness and self care

Anything by Diana Wynne Jones but i love all the Chrestomanci books - you can get them as a pack of 7 on kindle - and Howl's Moving Castle and it's sequel castle in the air are hilarious.

All the discworld books

Sherlock Holmes

Redwall books - animals in a medieval abbey

If she really is having trouble concentrating, audiobooks might be better?

I re- read The Secret Garden, Charlotte Sometimes, Tom’s Midnight Garden, I Capture the Castle.... when really ill with morning sickness. Found children’s classics easy to read but well written.

The mother daughter book club books are quite lightweight, set in a New England town and each focus’s slightly on a classic but more on the teenage girls lives in the book club. The box set would probably work out cheaper. I think I bought mine second hand from Amazon as even cheaper and some weren’t widely available in U.K. Covers are quite pretty.

If she’s reading that is a big positive.

My (adult) friend occasionally has stints in hospital for MH, she finds those mindfulness/ adult colouring books helpful for something to do when she doesn't have the concentration for or engagement with reading.

If she likes history/autobiography, Lark Rise to Candleford by Flora Thompson. Anything by Antonia Forest. Angela Brazil, if she’d like funny old school stories, free to download on Gutenberg. Chalet school. 💐🍫🍇

My previous avid reader son is suffering from NH and just can’t read at the moment.

My dd loved the Mother Daughter Book Club series at that age.

www.amazon.co.uk/Mother-Daughter-Book-Club-Quality/dp/1416970797/ref=mp_s_a_1_1?dchild=1&keywords=mother+daughter+book+club&sprefix=mother+daughter+book&tag=mumsnetforu03-21&qid=1595045466&sr=8-1

The Eagle of the Ninth is an easy read, with interesting characters and well written by Rosemary Sutcliff. If she’s read that already, there’re several follow on books, The Silver Branch, The Lantern Bearers are two, they stand alone, but are linked by family relationships. They would be good escapism I think.
If she’s reading more adult books, (it’s hard to know with a 13 year old !) she might like the Brother Cadfael medieval detective series, by Ellis Peters, it starts with One Corpse Too Many. There’s no sex or blood & gore or violence, most of them feature a clever teenage girl being rescued! Nicely written, with some humour.

Oh yes, another vote for I Capture the Castle.
I hope your lovely niece starts to recover very soon, poor girl.

Being miss nobody and jemima small versus the world by Tamsin winter have been very popular with my year 6 girls so should be relatively easy reading for a young teenager.

The Geek Girl books by Holly Smale are funny, sweet and undemanding and there are some bargains out there on boxed sets.

Steamborn series by Eric Asher - the kids reminded me of Harry Potter and Hermoine at their best. There are three books but are often sold as a bundle (the audible versions are excellent)

Wee Free Men (the whole Tiffany series), Dodger by Terry Pratchett (audible again fabulous)

Grand Sophie, Arabella by Georgette Heyer

Blue Castle by L M Montgomery

The Lark By E. Nesbit

Howl's Moving Castle, House of Many Ways, Conrads Fate, Dark Lord of Derkhelm, Enchanted Glass by Diana Wynne Jones

Hero's Guide to Saving your Kingdon by Christopher Healy (series of three). They are for all ages and very fun and a bit silly.

The Lark Shall Sing by Elizabeth Cadell

Adventures of Sally by PG Wodehouse

Most Robin McKinleys

John Green books

Depending on your budget, could you buy the cheapo kindle, and a voucher to allow your niece to choose her own books.

As a cheaper option, The Works have a good variety of book series at very reasonable prices.

Equal Rites or other Terry Pratchett books with the witches
Your Friend, Rebecca by Linda Hoy
PG Wodehouse
Some Miss Marple short stories
Bill Bryson's Notes from a Small Island, Neither Here nor There

I'm sorry she's not well and hope she gets better soon.

What age is she now?

Wishing you and your niece all the best - it can be so tough when a family members in hospital, you sound like a lovely aunt

The Sisterhood of the Travelling Pants is a lovely heartwarming one for teens about friendship and being apart from friends during the summer but connecting through a pair of "magic" jeans.

Ella Enchanted or anything by Gail Carson Levine if she's into fairytales - it's a fun retelling of Cinderella.

I Capture the Castle is a lovely coming of age novel by Dodie Smith (of 101 Dalmations fame).

Michael morpogo is another author my DD enjoyed

And the murder most unladylike series

My daughter loved Ann Marie Conway books - particularly Butterfly Summer. If you put that into Good Reads it will come up with similar books too. Good luck and hope she feels better soon.