First In Line is going to be difficult to explain because there is no information about it on their website so if my info is wrong, sorry. I signed up at a booth at ALA.
First In Line is a kind-of-subscription-box for librarians. Although it is from Underlined, it is Penguin Random House. Every couple of months you receive three ARCs and each ARC comes with samplers and display materials for librarians to put in their stacks. The books you receive are really book ARCs so if you are interested in this program, visit Underlined and sign up for the newsletter to get started!