[Replying years after the fact x3]
I only read this book once, years ago not too long after it first came out, but I remember being pretty impressed by it at the time. Although the book was incredibly long, the story was compelling enough for me that I didn't mind.
The aliens--being an Animorph fan from way back when, this was a fascinating concept for me. The idea that the aliens are actually "good," true pacifists who all get along and hate violence. (Yet of course there's this underlying factor of darkness, in what these aliens are actually doing without really realizing the evil they're perpetrating.) Wanda was an interesting character in that she did feel a little a differently from the pack, but seeing her thrown into a situation where she was surrounded by humans, you see how the influences of her race and culture, and how starkly different that makes her from them. And also, the idea of having the story be from an alien being's point of view, and seeing that alien learn about humans and come to care about them--there was something amazing about that journey that I really enjoyed.
However, what I probably responded the most to and loved the most about the book is what I like about all of Meyer's books, and that's the deeply emotional core. I hear people often complain that 'nothing happens' in her books (or that there's no plot), but I think what often people don't realize is that the key powerful moments of the books are not physical events but emotional ones. And for me, The Host had this in spades. (Jared's basically abusive treatment of Wanda when she first arrives was actually one of my favorite parts of the book, for how painful and horrible it was--even though Jared comes off as a 'jerk,' I felt like it was understandable, given the circumstances. It was his way of dealing with the sickening situation he was in; the girl he'd once loved shows up, but under the control of one of the alien enemy, and as far as he knows, the girl he knew no longer exists. And you can understand how crushed and alone Wanda feels, and her fear. Which makes the moments later on when she begins, bit by bit, to gain more acceptance all the more powerful. That sense of hopelessness and oppression being surrounded by humans who hated her race gave what happens later, her friendship with Jamie and later the rest of them, a greater sense of emotional release.)
Of course, the drama of Meyer's books can get so extreme it could fall into the realm of melodrama, and I think some of those moments could be seen that way. But, again, I personally kind of like that the books are willing to go that far to achieve that heightened drama, without that sense of self-consciousness that sometimes I feel reading other books. (That is, the sense that the author is afraid to do anything dramatic or emotional, lest they be accused of melodrama.) I like books with key powerful emotional moments.
I wasn't a huge fan of the romance, Meyer's type of romance isn't really typically to my tastes. (Either in Twilight, or here, though I do like the Twilight series, even if I understand why many people don't care for it. Though strangely I did like it in Life and Death, the gender-swapped reimagining of Twilight that came out with the tenth anniversary edition, or at least I liked the romance up through about the first half of the book.) Mainly, I just accept it as a point of the plot, which drives the plot and drama of the rest of the book, but I didn't have a particular interest in it.
It did seem strange to me that Wanda fell completely in love with Jared just based on Melenie's thoughts.
Yeah, I think it's established that Wanda's love for Jared is based entirely on Melanie's memory of him. I didn't have a problem with that, since Wanda and Melanie are sharing a mind, and Melanie's personality is pretty forceful as compared to Wanda's. In fact, one of the points in the book that I really liked was Wanda's sense of fear that her own personality might actually be being overridden by Melanie's, and someday Wanda would disappear completely--this was an important part of the book, as it helped Wanda begin to understand how the humans felt in having their minds taken over.