I have read Lewis' second book - the beginning is mysterious, spicy and compelling.
But that experience flattens as you go which makes the experience unbearable just in the middle of it.
Imagine you had a story for something like 100 pages but your editor tells you there is no way to sell a 100-page book thus you are trying to expand, to squeeze those 250 pages out of your story without being a jerk (by this I mean writing 'books' for adult children as Joko Wilink does. His LARGE elephant quotes and fonts with sexy pictures can turn an article into a book).
At times you succeed by grinding, by finding new comments and facts to include.
But more often you make people choke on an overabundance of facts they don't know how to prioritize and process.