A margin for murder / Lauren Elliott.

Enhanced descriptions from Syndetics:

In the riveting new mystery from the USA Today bestselling author, a murder and a missing first edition of Robert Louis Stevenson's A Child's Garden of Verses send rare bookstore owner Addie Greyborne on an investigation to challenge even the most distinguished of bibliophiles...

Addie leaves her Greyborne Harbor bookstore, Beyond the Page Books and Curios, in the capable hands of her assistant while she travels to the neighboring town of Pen Hollow to attend a book sale at a library that is closing due to lack of funding. But the real find is a bookmobile bus, which she's excited to refit as a traveling bookstore to hit all the summer festivals. The bookmobile also holds a surprising treasure- several classic first editions and an early edition of Robert Louis Stevenson's A Child's Garden of Verses .

But before the bookmobile can be delivered to Addie, a fatal car crash occurs. When an autopsy reveals poison in the victim's system and the first editions go missing, it's up to Addie to determine what would drive someone to murder. If she's not careful, however, she may be the next one to be dead on arrival . . .

"Plenty of specialized knowledge, local color, and romance."- Kirkus