The 'Gem' series by Kerstin Gier is a delightful trilogy that captured my imagination from the first page. The books, originally written in German as 'Edelstein-Trilogie,' include 'Ruby Red,' 'Sapphire Blue,' and 'Emerald Green.' I stumbled upon this series during a bookstore crawl, and the time-travel romance hooked me instantly. The way Gier blends historical elements with modern teenage drama feels fresh, especially with the protagonist Gwen's witty narration.
What I love most is how each book builds on the last—'Ruby Red' introduces the time-traveling gene, 'Sapphire Blue' dives deeper into the secret society drama, and 'Emerald Green' wraps up the mysteries with heart-pounding stakes. It’s rare to find a trilogy where every installment feels equally strong, but this one nails it. The English translations keep the charm intact, though I’ve heard the original German has even more playful language quirks.