Guy Gavriel Kay is the fantasy writer's fantasy writer. He served his apprenticeship co editing the Silmarillion, before going on to write a very fine pure fantasy trilogy, the Fionavar Tapestry, and then a sequence of books which although having a fantasy setting were clearly based on real episodes in the early medival history of Europe.
Tigana belongs in a sense to this second sequence. It's clear - and the author's afterword admits - that it takes as its starting point the Italy of the eleventh-twelth centuries - but this Italy has suffered more sea change than the Spain of The Lions of Al Rassan, for example; on Kay's spectrum from fantasy to history this lies nearer the fantasy end.
It revisits a character - not an individual, but a type - who appears repeatedly in Kay's fiction: the brilliant, handsome polymath prince, Diarmuid in Fionavar, Bertran in A Song for Arbonne, Alessan here. I'm still not clear why Kay needs to revisit this character again and again...
The characters are well-drawn, complex and engaging (even the villains); the backstory is clearly deep, and the setting very well presented and portrayed with a wealth of detail. The writing is lyrical, engrossing and persuasive.
This is story telling of a very high order, investigating themes of tyrrany, loyalty and love. Don't read this (or, indeed, any other of Kay's books) if you want an easy read or a happy ending; but if you care to use the lens of fantasy to see reality more clearly, more intensely and more painfully, then this is a very fine book.