I actually found her 'Memoir by Lady Trent' series to be more rewarding on a re-read than the first time through. The initial book, 'A Natural History of Dragons', charmed me immediately, but it was the way Brennan built the world across the sequels—the politics, the different cultures, the slow-burn scientific discoveries—that really cemented it as a favorite. It’ invigorating to see a fantasy protagonist whose primary weapon is her notebook and her intellect.
Outside of that series, I'm less familiar, though 'Turning Darkness Into Light' is a lovely epistolary-style continuation set a generation later. It channels that same academic detective-work vibe. Her 'Onyx Court' books, set in historical London with faeries, have a dedicated following but never quite clicked with me the same way; the tone felt a bit more... constrained, maybe?