My favorites are All Souls, a fictional account of Marías's sabbatical at Oxford, which manages to movingly evoke (and invoke) an outsider's experiences in that strange, hermetic world and possess a far greater depth than its pages at first reveal, and the disarmingly memoiristic Dark Back of Time, which at first seems to be an analytical exploration of the earlier Oxford book before it dissolves or expands into a far more complex and elusive text about fiction, narration and authorship. The only book of Marías's that I've read--or more like stumbled through--in Spanish is Vidas escritas, a colorful--and fairly easy to read--series of capsuled ruminations on writers such as Dostoyevsky, Kafka, and Faulkner, so I can't speak to the quality of the translations, from all the reviews I've seen, his regular English translator, Margaret Jull Costa, is superb.
Your Face Tomorrow: Fever and Spear on first glance seems to be a departure; it's billed as a kind of spy or detective novel, whose protagonist, Jaime (or Jacques or Jack) Deza, recently separated from his wife, finds himself being recruited for the British secret service. But almost immediately many of Marías's touchstones pop up: the recruiter is none other than a retired Oxford don; the narrator's voice unfolds in ponderous, yet charged serpentine curls; and history (or History), ever present in the previous novels, plays a determined role here. I haven't gotten that far, so I can't say much about how this first book in the trilogy functions on its own, but the reviews suggest that it does hold up quite well, guiding you right into book number two (Dance and Dream), which I also look forward to reading. Marías supposedly is writing the third volume right now.
Being a truly contemporary author, he has a fabulous Website (which is almost completely in Spanish, except for one page with hyperlinks to essays on his writing, interviews and reviews), chock-full of information on his work and life, and best of all, a very chatty blog!
Here are the opening sentences of Your Face Tomorrow: Fever and Spear, which gives a sense of Marías's style and thematic concerns, and the rich vein of possibilities they both hold and discharge:
One should never tell anyone anything or give information or pass on stories or make people remember beings who have never existed or trodden the earth or traversed the world, or who, having done so, are now almost safe in uncertain, one-eyed oblivion.