Setting the book on Earth, with normal characters in an apocalyptic situation, also allows the author to show relatable people going through extraordinary circumstances. This can bring the reader further into the story, especially if they can find analogues to their own self in one of the characters of the book.
The primary conflict that the protagonist faces is the issue of divided loyalties, on many levels. First, Wanda is allied with the Seekers and the rest of her people; however, she finds herself becoming more and more sympathetic to Melanie. Then, she has to decide whether or not she is really with the humans or should remain with her people. After that, there develops a divided loyalty between Jared and Ian, as she starts to develop feelings for both of them. All of these varying conflicts mean that Wanda tends to be passed along from side to side by many different forces, never really settling completely on one allegiance before circumstances tear her toward someone else.
The love triangle also brings to mind the main conflict of the character. As Wanda does not make a tremendously proactive impact on the actual conflict between the souls and the humans so far, she has to mostly deal with Jared and Ian's affections, and the fact that their respective loves share the same body.
In terms of doubts about the novel, I presume that this term is meant to ask for negative things I have in mind about the book. For one, I feel that the overall premise is interesting, but it would have been nice to explore the world a bit more. As of right now, all this setup deals with is this single mind in this single girl, and a few humans that she runs into (who all coincidentally happen to be the girl's family and boyfriend). It would have been nice if the grander scheme of the alien invasion and the alien world was presented with a lens outside this single protagonist.
What's more, I feel the love story to be a bit contrived and forced; the character of Jared could have just as easily been someone else, or even someone appealing for which Wanda would legitimately fall in love. As it stands now, however, his introduction and first impression leans far too heavily toward his hostility and threats to kill Wanda. This makes it completely unbelievable that Wanda would legitimately fall in love with him, and Melanie to remain in love with him.
The name of the book - "The Host" - is very significant for a number of reasons. On the surface, it is the tale of a literal 'host' body that the protagonist inhabits. Melanie's body houses Wanda, but it also houses Melanie's personality as well. Eventually Melanie does so willingly, thus bringing forward the more commonly used term for 'host,' as someone who welcomes you into their home or other establishment. At the same time, there is a somewhat hostile connotation to the word 'host' in the context of invasion, reminding the reader that, effectively, Wanda is an alien creature that is invading a human girl's body.
In terms of hosting, Jeb also welcomes Wanda into the camp, where she begins to feel welcome. As previously mentioned, this parallels the physical infiltration of Wanda, as Melanie/Wanda infiltrates and is hosted by the camp itself. The title brings to mind the theme of invasion and identity - what is our mind, and what is our body? Do we have a real connection to these things, or are our minds merely hosted by our bodies? What makes us human: the sum of our parts or what is contained in the mind?
If I were to relate the novel to today's events, I would likely state that the issues involved are identical to those of the last unit - there is an element of the War on Terror as well, but from the other side of the equation. In this book, the protagonists are the ones hiding in caves, sending out small raids and carrying blind hatred for those who have attacked them, while the antagonists are the ones sitting in cities and comfortable lives. By showing just how dire their plight is, it is easy to see the level to which terrorists could hate an industrialized society that seeks to kill them - of course, there is the question of who really fired the first shot, both in this book and the real world.
The issues with Walter and the Seeker (as well as the conflict about whether or not to remove the soul) deals with euthanasia. In both instances, there are reasons for putting the characters out of their misery - Walter is sick with cancer and suffering in pain, while the Seeker knows where they are and is an important enemy to dispatch. The debate regarding the latter rages when Wanda reveals she knows how to safely remove a soul without killing the Seeker. The question becomes, do they do it? And if they do, dare they risk letting the soul live?
I do not really enjoy Wanda's lack of proactivity. Much like many Meyer female protagonists, Wanda seems to be pretty helpless and whiny; only when it really matters to the plot does she do something, and by that point the reader is sick of her constant navel-gazing. I understand when a character is vulnerable, but she spends too much time doing too little, with things just happening to her, to make her a strong protagonist. There are far too many things she seems to stumble onto, and she has a hard time speaking up for herself; Jamie or Ian has to do it for her. In this way, she is less of a proactive character and more of a doormat, which does not make for compelling reading.
I suppose I have a very negative reaction to Wanda at times because she does not seem all that alien a character. I was hoping for more of an adjustment, a culture clash, but it just seems like there are two human girls, one of which knows a lot about other alien worlds, in one body. If her personality were to be a bit different, it would be much more interesting.
I had a very sour emotional reaction to the development of the Ian/Jared/Melanie/Wanda storyline. I still have a hard time believing that Jared remains an appealing figure, even after his apparent change of heart. However, I am beginning to see and relate to what she is going through. When two people vie for your affections, it almost seems as if two different sides of yourself favor each of your options. There is one part of you that likes the one, and another part of you that likes the other. In this way, I thought it was an interesting parallel, but I thought it took too long to get there.