I will answer your question completely, and try to address each point.
As for her reading the novel, in and of itself, by itself... One can't really get mad at her for reading fiction, any more than they can be mad at guys for watching porn about gangbangs, hot 18 year old sexy teens squirting, etc. Lol. Women are emotional, men are visual, this is nature.
As for "Is she cheating?": I'm divided on the "Is she probably cheating?" question *but only as it relates to the romantic/cheating novels*. For one, her reading those novels COULD indicate she wants to cheat. However, it could also be argued that "If she was cheating, why would she need to read a damn book about it? She could be ACTUALLY DOING IT." So really, that question goes both ways.
However, she's likely cheating but based on other criteria and the fact that 50% of wives cheat in general, especially sketchy ones. Read on.
If she cheated on you before you got married though, that definitely shows she's a cheater and disloyal. The only question is, how badly and how often will she be disloyal? Also, cheaters always will try to downplay their cheating. If she admits to kissing him, then it really means she did some making out and touching (at the very least), and she MOST LIKELY went all the way and had some wild raunchy sex with him. She probably felt guilty (or felt she'd be caught) so she wanted to ease her guilt by "confessing"... but, like most women, she confesses to a much lesser crime, to make you think less bad of her and make you less likely to dump her before the wedding.
Ultimately, I think it's likely she's cheating (I mean, half of all married women cheat, so your wife is definitely more than 50% likely to be cheating, based on what you said here).
HOWEVER, the real question is, what can you prove in court? And secondly, DO YOU want to divorce her? Do you even WANT to know if she's cheating? Is your goal that, by catching her and confronting her, you can regain some control in the relationship and prevent her from cheating in the future by taking proactive steps to monitor her behavior so that she cant cheat sneakily? (This actually is a good idea, and I actually do all of this to stop my husband from cheating, and it works. Read on to find out what I'm talking about specifically.)
IF you want to know, then hire a private investigator. Then you can either cheat on her back without feeling bad or worrying she could use it as a reason to dump you... (just consider it a "secret open marriage"...) OR, you could use it to divorce her... OR, you could confront her with it and use it to regain some control of the marriage.
Some good ways to regain control of the marriage is to basically say "Hey babe, I found you cheating. Here's the proof. We have 2 options here. 1, I divorce you and take everything, or worse, I'll annul the marriage based on marriage fraud since you never loved me. Or 2, if you genuinely want to change, and genuinely admit you have a sex/cheating addiction and want to change and be a good person, then you will WILLINGLY allow me to have some proof and reassurance you're not cheating, by letting me do a few steps."
The steps should be:
-She doesn't go places without you, without you approving and knowing exactly where she is going. NO SECRETS. Not even on casual trips or driving. Period.
-You guys both buy iphones, so you can track her location at all times via the "Find my Iphone" app. and if she has the audacity or stupidity to turn her "find my iphone location" off, then you AUTOMATICALLY KNOW AND ASSUME that she is cheating. And she will be punished accordingly.
-She doesnt go out with female friends without you. She doesnt go visit friends without you, especially late at night. She only hangs with female friends for respectable events, during the daytime, and you are free to come along at any time. And if she doesnt allow you to come, then shes not allowed to go, plain and simple. (And if she CLAIMS her friends wont allow you to come, then its the same result, you dont allow her to go.)
-She allows you to download MOBISTEALTH on her phone, which allows you to see ALL of her app data, her texting and calling data, etc.
-She allows you to have a password "parental control" on her phone, which prevents her from downloading OR deleting apps, without YOU inputting that hidden code. (This way, it stops her from, for example, being able to download Tinder when you're not around, and then delete it before she comes back home. This way, she cant install or remove any phone programs without you.)
-You monitor all the credit and debit card bills and NOT letting her have any cash in hand to use (I recommend only using debit not credit for good financial success purposes LOL, only use credit cards in tiny amounts to build credit, but try to live below your means, save and invest, and only spend in cash/debit (in her case just debit since she is not trustworthy), but that's a topic for another answer). The purpose of monitoring all cards and bills is to prevent her from, for example, buying a secret phone, or paying a male gigolo, or doing anything unscrupulous with her money that you would want to know about.
IF SHE AGREES TO ALL THESE TERMS, THEN YOU KEEP HER... IF NOT, THEN YOU DUMP HER...
but IT ALL STARTS WITH GETTING SOME LEGAL PROOF OF HER CHEATING. YOU WILL NEED TO PAY A PRIVATE INVESTIGATOR. (PAY IN CASH SO SHE DOESNT KNOW THAT YOU ARE ON TO HER.) IF YOU DONT GET SOME DOCUMENTED VIDEO AND PHOTO PROOF OF HER CHEATING, THEN YOU WONT BE ABLE TO ENFORCE THIS.
(Note: I dont cheat on my husband back, and he hasnt cheated ever since we got married, but he cheated when dating. I dont recommend cheating to "get even". But if she did cheat, I know that some men feel they need to "get even" at least once to retain their manhood. If you feel that way, then do it, and be up front with her from day 1. "Honey, also a condition is that I get sex from someone else JUST ONE TIME, since you already cheated yourself. If you can dish it, you can take it. I cannot remain in the marriage if you are gonna f*ck other men and then not let me f*ck another woman just one time so that we are even, fair and square. I hope that is ok with you. If not, too bad, you shouldnt have cheated if you dont like that." HOWEVER AGAIN... I'm not sure that will solve anything long term, but for men, sometimes it just feels so damn good that they have to. )