There aren't many books that I'm an evangelist for. I'll tell you what I like, and I'll make suggestions and recommendations, but I don't often state outright that "You HAVE to read this." I will go out on that limb for The Sparrow, though. You have to read this.
This is a very hard book to pigeonhole. You may not care for science fiction; this is SF free of technobabble. While the primary plot concerns interplanetary exploration and first contact with a non-human species in another solar system, the focus is on character and the setting doesn't require contortion of the imagination. You may be wary of fiction with religious overtones; this novel prominently features several Jesuit priests among its characters, but the last thing it does is preach. The novel explores Big Ideas of faith and God and humanity and Meaning in the way that many of us would - in far-ranging conversations with friends - and doesn't beat you over the head with them. You'd never guess that this is Mary Doria Russell's first novel (previously, she wrote scientific articles and technical manuals); the writing is very accomplished, and yet it doesn't call attention to itself at all. What other arguments can I shoot down for you?
If you have issues with "spoilers," you may be taken aback by how much Russell tells the reader in the early chapters of the book. After a radio telescope picked up transmissions that resembled music from somewhere near Alpha Centauri, an expedition to find out more about where they came from was facilitated by the Jesuits. Something VERY BAD happened there, and only one member of the party was left to return to Earth. That survivor, Father Emilio Sandoz, has been deeply wounded in every possible way, and resists his order's efforts to understand what happened on the planet Rakhat. Having believed that he and his fellow expeditioners had been drawn there by God, Emilio can't fully understand it himself.
Knowing all of this fairly early in the game doesn't lessen the novel's dramatic tension one bit, or blunt the impact of the full revelations that Russell eventually makes. When I reached the end of The Sparrow, I was drained - and I had read the book once before! That's just how masterful Russell's writing is.
And while Russell's plot will certainly hold your attention, it's the fully-realized characters she has created that bring you through it. The characters have stuck with me during the five years since I first read The Sparrow, and I was once again struck by how vividly drawn they were. The dialogue and interaction between them feels absolutely true to life, even when they're discussing questions of belief or problems of engineering, and I love the way Russell has given them humor. My favorite character is Dr. Anne Edwards, brilliant and blunt, with astronomer Jimmy Quinn, "discoverer" of Rakhat, a close second. Emilio Sandoz - priest, linguist, cultural explorer, perpetrator or victim of a tragic misunderstanding - is absolutely central to the story, but I did find him enigmatic at times and therefore harder to embrace than some of the other characters. I wonder if that was Russell's intention. However, what's especially striking to me is that while not all of the characters are necessarily likable, I think she has rendered them all sympathetically - even the non-human ones.
I tend to have some trouble visualizing imaginary species. That's one reason I tend to get my science fiction and fantasy from movies and TV instead of books, and despite Russell's strong descriptions, I don't have a strong sense of what the Runa and Jana'ata natives of Rakhat are supposed to look like...but I'm not sure it matters. Russell does convey that they're clearly different from humans, while she also explores the ways in which they're not so alien.
The Sparrow is a page-turner that will make you think critically, make you feel deeply...and make you want to talk about it with other readers.