What is a good way to say that a book is a light read? By that I mean writing that is basically created for entertainment, doesn't contain much drama and isn't particularly thought-provoking. Preferably not in a condescending tone (so not like "trashy literature"). One pharse I've heard is 元気が出る本 but maybe that's a little different from what I'm describing. I believe ライトノベル is not the right term either because from what I've read some of them can be quite serious.
How about 気楽【きらく】 or 気軽【きがる】 (na-adjectives)? These words imply that the content is not so serious nor thought-provoking.
Another option would be 手軽【てがる】 (na-adjective), although this may tend to imply the volume of the content (ie, the number of words in a book) is small.
As you already know, ライトノベル refers to a certain genre of novel mainly targeted at otaku. They are basically 気軽 but not always so.
You could possibly say that a book is 読みやすい, meaning easy to read. That wouldn't carry the connotation of a certain kind of book, but lets you know that it's not super dense.