Gamebooks have always utilised a wide range of methods to determine success or failure, ranging from random rolls to trivia quizzes to riddles to maths problems, but they also included minigames. I'm going to try to define it as a game that is not the main part of the gamebook, but a separate challenge that is used to determine success or failure. Now, I could spend ages trying to define what a game is, but I will trust your own idea on that and if you would like to know more, I will refer you to the modern Library of Alexandria.
There were occasional minigames in paper gamebooks, such as Curse of the Mummy, where you had to work out which move you should make in a boardgame. The Forgotten spell also includes minigames.
However, the introduction of gamebook apps has made minigames possible. For example, Warlock's Bounty is a gamebook app where combat is decided with Magic the Gathering style cards, the Khare app from Inkle has a game called Swindlestones and the 8th Continent by Patrick Garrett has several mini games - combat is card based, finding things involves playing a version of bejewelled and reading your father's journal involves working out a code.
This got me thinking about minigames and their use. I like mini games in books as it is something to focus on and work out. It provides an intellectual challenge that depends on skill which is refreshing if most things are determined randomly or by choices you make which have consequences which have some degree of arbitrariness.
I have found one issue with mini games however. Games which have no variance - you have to do the same thing to win - and don't allow you to skip them become a waste of time. It is fine in Warlock's Bounty where every combat will be different based on the randomly drawn cards, but if I know how to crack a game every time, I no longer want to play it.