There are some cool online tools to help check the details of a manuscript, including readability. Here’s how 3 WISE MEN scored (green is good):
PS: When writing a high school textbook for 15 year olds, the readability was set about the same – a target group of 12 year olds. It was heartening to have Allan, my good friend and editor, read a chapter of 3 WISE MEN to his 12 year old granddaughter and learn that she enjoyed it and wanted him to read more! Although this novel has an acceptable readability score, it still contains some complex ideas, as well as a few foreign words – suited to a more mature audience.