Wither is different from the action-packed trilogies like Divergent and Hunger Games. It's a much "quieter" book, if that's the right word. While DeStefano is dealing with a crumbling society devastated by a cure for cancer which has ended up decimating the population by causing new generations to die at young ages, there is less action and violence than some of the big selling YA dystopias. Wither is more of a "relationship story" in many ways. The heroine Rhine has been kidnapped to be one of a harem of three wives to a rich man which is typical of this society. There's more to the man and his mansion (and his gruesome evil scientist dad) than I'm giving away here, but the focus of the book is on Rhine's relationships with those around her - her "sister wives", her husband-by-enforced marriage, her lost brother and parents, and her growing fondness for a servant in the mansion.
The story deals with concepts of trust, guilt, and innocence but does so in a relatively sedate way. Most of the action takes place hidden away behind the gates of the mansion - a relatively sterile and manicured environment. While we get a few glimpses of the world outside from Rhine's past and from brief forays into the "real world", the bulk of the action is focused on a small group of people in a contained environment. So in many ways the book reads like the social experiment that it is.
I haven't read either of the sequels yet so I can't comment on whether those are more action-packed, but if you're wanting adventure and action, this isn't the book for you. However, if you want a thoughtful exploration of what life might be like when the human race is on the verge of extinction and the questions are whether or not it's worth forming meaningful relationships and striving for freedom and a future, this is a great read. Not much in the way of explicit sex or violence so highly suitable for younger readers (although there are allusions to gory stuff, nothing too horrible appears on the page). The writing style is smooth and the characters and situations engaging. An interesting departure in an otherwise more action-packed genre.