Trouble Pug is free-to-own for Kindle today and tomorrow.
These books may also be read for free on Kindle Unlimited, but only for a limited time. On or about September 16 they will go out of that program so that they can again be offered at outlets other than Amazon in ebook form.
Notes From Hiding and Trouble Pug are also available in trade paperback.
Notes From Hiding's main characters are teens who'd been born about the time The Hidden ends. Other books set in the same dystopian world that's shakily returning to freedom are The Smolder, The Birdwatcher, The Unexpecteds, and The Historian. While there's a little overlap with some of the books, each book has different characters, and books are set in various locations.
Trouble Pug, a story of two girls working at staying friends despite their differences and difficult circumstances, features a bit of time travel (which accounts for some of the difficult circumstances - hello, getting caught as stowaways on the Lusitania on May 7, 1915!).