Without knowing the book by Robert Lopez I think you will be in for some problems using it with Maple 2020.
I have in my hand right now another book prepared using Maple V Release 3: Robert M. Corless, Essential Maple (1995).
If you are just starting out using Maple, don't use the book now, but put it on the shelf for another time.
If you are well versed in Maple already you probably wouldn't be asking the question. Surely, you can learn something from the book, but you will have to know that important changes have happened since that release.
Among the important ones and not necessarily in sequence of priority:
1. The ditto (") in Release 3 is now (%). This happened when actual strings were introduced.
2. The linalg package has been superseded by the LinearAlgebra package, but is still availabe in 2020.
3. The appearance of readlib commands may confuse you. Not used anymore.
4. The default graphical user interface (GUI) is now set to Document mode and 2-D math input. This I advise you to set to Worksheet mode and 1-D mat input (aka. Maple input) . That way the GUI in 2020 looks more like the GUI in Release 3.
But, obviously, lots of other changes, enlargements, and improvements have been made since Release 3.
PS. Another book on my shelf, Robert B. Israel: Calculus The Maple Way has the following footnote in its Preface: " Note, however, that Release 4 requires at least 8 MB of RAM, while Release 3 can manage fairly well with 4 MB." (Yes MB, not GB).