It's really important to get kids to develop their confidence in their reading skills early on. One of the best ways to do this is to give them each a small amount of reading to do out loud. Assign each child a character or simply pass the book around at the end of each page. Make sure all the kids are patient and do not tolerate any making fun of slower readers. Let them spell out any words they don't know.
At the end of each chapter, ask the group questions on the part of story that has just happened. Kids like to compete and will make an effort to stretch their memories. Ask about who said what, who did what and where. Ask them how it relates to previous chapters as well. This will focus their attention and help them listen and read actively instead of passively.
Push the engagement further by getting the group to engage imaginatively with the text. Get them to discuss what they would do in the positions of the characters and who they support in the story the most. Talk about what the characters would do after the story has ended. You can even get the group to perform a play.
Encourage the children to put their hands up and say when there is a word they do not know. Let other children have a go at saying what it means. If they don't now, get them to collect a list of all the words then share them with the group. Each will be responsible for finding out some of the words and reporting back.