What's the first noteworthy Gothic book? Have you read it, and would you recommend it?

Whether it was the first Gothic book ever written, I cannot say, but the first Gothic to be recognized as such was "The Castle of Otranto" by Horace Walpole. It started the Gothic frenzy in the 18th century, which has evolved over the years and seems to have remained popular even today. I only read it recently and I would definitely recommend it to anyone interested in Gothics. Not only as a literary piece, but for pleasure-reading as well.

I haven't read it, but I'm going to now. I bet it is a good book, but it will also be great to see what started it all.

Yes, it is a good book, but my complaint with some of the older books is that the language can be difficult to follow sometimes.

I've noticed that, not just with gothics too. For example, even reading Shakespeare's plays is hard for me due to the language. I wonder if anyone will ever take these older books and "translate" them into modern English.

Since Walpole's CASTLE OF OTRANTO was first printed in 1529, I would surprised if it weren't the first notable one. I do not find them hard to read. They are not written like Shakespeare's plays.