What are some textbook that contain material about monoidal categories and monoid objects? I have seen Awodey's and Riehl's books and they don't seem to cover this part, while Mac Lane is way too dense to be used for my course. I accept even other kind of sources, like sites or online lectures, but I have to exclude nLab because it uses higher category theory.
Specific reference request for category theory
category-theoryreference-request
Best Answer
Here are some resources on monoidal categories (including monoid objects) which I found quite useful and detailed as a beginner:
Borceux "only" treats bicategories, but monoidal categories are just one-object bicategories, and general bicategories are not much more difficult to understand.
In case you know German, you can also check out my book which treats monoidal categories in depth.