Ian Parker (2004). Slavoj Zizek: A Critical Introduction.Pluto Press (Modern European Thinkers) . ISBN-13: 978-0745320717
A classical book but still interesting according an overview of the complexity of Zizek thought
Sean Sheehan (2012). Zizek: A Guide for the Perplexed. Bloomsbury Academic. ISBN-13: 978-1441180872
Unpacking the philosophical references that fill Zizek's writings, the book explores his main influences, i.e. Lacan, Kant, Hegel and Marx and the way he managed with them to read the contemporary world.
Massive question. I am not certain it has. I think his conception of ideology is as it is, but he has found others ways to talk about it. If I may be so bold, my recent paper in the Zizek journal covers one aspect of this: here is the link to the issue - Vol 16, No 1 (2022) (zizekstudies.org)