Books/Notes recommendation request: Multivalued functions/Riemann surfaces

The book by Otto Forster on Riemann Surfaces is pretty good. I never finished reading it myself, but it covers things like Riemann-Roch and Abel's theorem from a sheafish viewpoint. In particular, the proof of Riemann-Roch is analogous to the one in Hartshorne; it follows from the Serre duality theorem and an inductive argument. Learning about sheaves is definitely a plus.

Also, there's a book by Springer, though the level is a bit more elementary.

Not being trained in Mathematics, I have the distinct impression that the British book by S. Donaldson (Oxford University Press) is the easiest to read.

I am not claiming it is the very best in terms of breadth and depth of knowledge in an attempt to acquire a fairly decent understanding of Riemann Surfaces, but I am impressed that at least a retired engineer (with graduate degrees in Electrical Engineering) like me, not being ingrained in topological concepts, can start reading his book here. Even the classic work by George Springer (Indiana University) can be challenging in that the writings after the third chapter can be daunting to those without the proper background and prerequisites, i.e., Real and Complex Analysis and Introductory Topology.

There may be other ones out there I am unaware of. That is just my two cents here.