An excellent resource to begin with is Hal Varian's book: Information Rules.
You can find this on Amazon here:
The book was published in 1998, and hence some chapters may be a bit dated. But although the software landscape may have changed, most basic rules still remain the same. The book discusses the key elements of software pricing: versioning, bundling, switching costs etc in detail.
You can also purchase individual chapters that you are interested in. These are available as HBR case studies. But considering that a used edition is available for less than $5, you may want to buy it from Amazon.
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