I got this free download in a fit of guilt for buying too many books for my Kindle. I love Miss Marple stories, and this is superficially a similar concept - little old lady, mild-mannered and almost ignored by the world at large (hence the 'invisible' of the title), investigating the disappearance of a neighbour and single-handedly solving the crime.
The plot is fairly basic and unimaginative, but the author spins it out nicely into a very readable yarn, stringing the reader along with great skill to keep turning the pages. The characters all have a certain charm, and I couldn't help rooting for Ivy herself. And there's a nice level of dry humour as well, which I always appreciate.
I would probably not have read this if I'd known it was a 'Christian' book, but on the whole the religious element is low-key and in keeping with the protagonist's age and situation. There are two or three places where she turns preachy, but it's easy enough to skip over those parts. And it's refreshing to read a book with no swearing, gratuitous sex or gruesome violence.
A nice, easy read at a great price!