The standard cliché regarding sentence lengths in a novel is to vary them, to keep the reader interested in the action. I agree, but with this caveat–the sentence lengths and variation should also suit the pace of the plot. For example, in my latest novel, sentences are longer when the pace is slower, and shorter when the action or drama increases. The following illustrates this contrast (using ProWritingAid). You can guess which chapter contains fast—paced action and which is slower? This will why I ignored the red dot warning in in chapter 15! Such analysis is a useful guide to writers.
sentence length
Variety – the spice of reading
Experts agree – the length of sentences must vary to hold a reader’s interest. That is, unless you intentionally want to put them to sleep! Here is an analysis of the first 100 sentence lengths from 3 WISE MEN…
Note: this analysis was flat-lining until I took out the Acknowledgements, Dedication and Chapter index!