Shelley
Shelley asked Maria V. Snyder:

I've read Poison Study, which I really enjoyed. Planning to continue the series, I know you've just released another book about Yelena and Valek. Should I read the Study series then the new book? Or are there other parts of the story in another series? Thanks! : )

Maria V. Snyder To get the full experience and see what Yelena and Valek are doing between Fire Study and Shadow Study (the new book), I'd suggest you read the Glass books (about Opal Cowan).
Storm Glass
Sea Glass
Spy Glass
Y and V have various levels of involvement in the Glass books (Valek has a big role in Spy Glass - no surprise ;), but you don't have to read the Glass books to understand what's going in Shadow Study.
And I also suggest you read Ice Study before Shadow Study - it's a free short story and a bit of a prequel to Shadow. Here's the link: http://www.mariavsnyder.com/IceStudy.php

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