"Work" (noun) is plural or singular?

Solution 1:

Work can be either singular or plural, and in your context, either is possible - but the pronoun must agree, in either case.

So you can either use

• I provide a high-level overview of the previous work, including its limitations.

or

• I provide a high-level overview of the previous works, including their limitations.

In the first case, you refer to the entire body of previous work, whereas in the second, you refer to multiple instances of previous works. The difference is subtle, though, and my initial point stands - I'd say that you can use either, as long as the pronoun is consistent.