Every mystery book has a detective and half of them have cryptic messages. You're gonna need to give more than a lighthouse and a 'G' if you really want to find this book. Good luck with that.

Could this be an older book? Agatha Christie has a mystery involving a lighthouse - 'Evil Under the Sun.' Though the 'G' author detail doesn't fit...unless we're tricked by a middle name or something.

idk the book but the author starting with 'G' made me think of Elizabeth George? she writes mystery but idk if she wrote something with a lighthouse. worth a shot?

The inclusion of a lighthouse is making me think of something Gothic. It's not a perfect fit, but maybe you're blending memories? There's 'The Shadow of the Wind' by Carlos Ruiz Zafón, which has a lot of mystery and thriller elements. Misremembered 'Z' as a 'G' perhaps?

Ok the lighthouse is definitely a key detail here. Could it be one of the Alex Grecian books? He wrote 'The Yard' and other Victorian crime novels. Lighthouses aren't exactly his general thing, but authors can switch it up, you know? Gonna have to do a bit more sleuthing on this one.

There's this one book I remember with a lighthouse - was it called 'Beacon of Fear' or something? Can't recall the author but pretty sure his name was Gordon or Gerald? Wish I could be more help, that lighthouse part just really stuck with me!

i dont know the book but now i wanna read it too lol, gonna wait here and see if anyone knows

Sounds familiar... Could it be 'The Lighthouse' by P.D. James? It's been a while since I've read it, but I remember there was a sinister vibe, a detective, and definitely a lighthouse. And James' writing always has that cryptic feel. Worth checking out!