I have been trying to study elliptic functions and theta function for quite some time and have already got the hang of the classical theory (Jacobi/Ramanujan) based on real analysis, and now would like to study the arithmetical part related to imaginary quadratic fields and their relation to elliptic functions. Having very limited knowledge of Group Theory and Galois Theory (and things covered under Modern/Abstract Algebra) I tried to find classical references and stumbled upon Weber's Algebra, but unfortunately it is in German. Does anyone know if an English translation exists and if so how can it be obtained?
If there is no English translation available can someone point out any good references for "Imaginary quadratic fields and their relation to elliptic functions" keeping in view my very limited knowledge of Abstract Algebra.
This is a very deep subject which continues to be pivotal in contemporary number theory. I've never read Weber carefully, but my impression is that his arguments are difficult to follow and regarded as somewhat incomplete. For example, in his solution of the class number one problem, Heegner cited some of Weber's results, and my sense is that one of the reasons that people originally rejected Heegner's argument was that these resuls of Weber were regarded as unproved.
There is a survey by Brian Birch from the late 60s where he goes over the results of Weber that Heegner uses and shows why they are all valid (and hence why Heegner's argument is valid); his arguments use class field theory.
In general, I'm not sure that you can learn all that much about this subject without learning some Galois theory and algebraic number theory; indeed, proving the relationships between quad. imag. fields and elliptic functions was one of the driving forces in the invention of algebraic number theory and class field theory.
You could try the book of Cox, Primes of the form $x^2 + n y^2$, which surveys some of this material. I would guess that it uses more algebraic number theory than you would be comfortable with, but perhaps it will give you some hints.
There is also the book $\pi$ and the AGM by the Borwein brothers, which gives a very eclectic survey of some this material. The proofs are both elementary and (often) quite unusual from a modern, systematic point of view. But they may be more accessible to you, and it is an amazing book with a lot packed into it.