Is one allowed to read Jewish novels on Shabbos?
If there is any סרך קדושה (a slight amount of holiness) discussed in these books, like lessons you can take from it, be it Yiras Shamayim or some other wisdom, there is room for leniency.
In any case, it is proper to only read books on Shabbos which are of Torah and instill fear of Heaven.
See here as well:
See also Halacha2go article #99.
ראה המצוין שם בהלינק, וראה גם קצה”ש סי’ קז סעיף כו-כז וסקמ”ג.