Through a Looking Glass Darkly by Jake Fior.
Published by Alice Looking (1 Jan. 2021)
ISBN-13 : 978-1527256903
ISBN-10 : 1527256901
Sold via the Alice Through the Looking Glass shop on Cecil Court, London WC2, and also available on Amazon… but I got my copy at the V&A Alice exhibition.
From the dust jacket blurb:
Through a Looking Glass Darkly is a deeply layered hypnotic journey to the dark side of Carroll’s original text.
If Through the Looking Glass is Carroll’s mirror image of Wonderland, then Fior’s new novel, ‘Through A Looking Glass Darkly’ , is the mirror crack’d.
The V&A website:
The debut novel by Jake Fior features a dual narrative, interweaving details of Victorian magical societies with an updated narrative based on Lewis Carroll’s original text. A teenage Alice embarks on a journey of self-discovery as she steps through the looking glass into a distorted reflection of the modern world.
Now, I’ve not yet read the book, but the cover says there are ‘New Illustrations by John Tenniel’: they look to me suspiciously like the original ones, coloured and sometimes altered. I mean, I like them, but I’m not sure they’re new- maybe I’m missing something.
Alice in the Internet 
I was at Alice through the Looking Glass book shop in London back in November. He explained that the ‘new’ illustrations are from Tenniel’s sketch book that is part of his collection (the sketch book was also on display at the V&A.. you prob saw it there too).
The sketchs are like you said mostly versions of the illustration we all know, but he considers them new, since they were never pubblished in any books.