I would suggest that ecommerce is so much more than a specific technology. ECom is more about how the database is built and the features that are required. There is a good book that I read 10 years (a long time) ago that goes into ecommerce with asp classic. But there are many new ones using newer technologies here.
The big key is how you structure your data, products, options, orders, order details, credit card/user data, etc. Also, the various ways of processing transactions. How to handle order pipelines. When to offer navigations away from the current page and when not too. How to make product recommendations. Dealing with tax API's and shipping API's. You might consider downloading DashCommerce (a .net application) or something similar that fits your preferred technologies to see how they have set things up. Install something. Get it set up to feel the pains for data management. ...also to feel the pains of navigating a shopping cart (adding products to the cart, updating the cart, checking out, setting up an account or having an anonymous checkouts).
Being an commerce developer generally means knowing how to work with Verisign (now paypal) or similar payment processing. How to intercept fraudulent transactions and deal with them appropriately. How to work in a high transaction environment (caching, tierd architectures, queues, web services). Cross linking products based on user history/profiling to maximize transactions (think candy at the check out stand of a grocery store). Knowing how to work in a secure manner with sensitive data which generally means encryption techniques, setting up DMZ's, working with proxies, etc. Take a look at using some form of a rule engine for order pipelines so that your business rules are separate from your application logic. Understand coupons schemes, discounts, etc. Frequently ad campaigns are heavily used for generating side income.
Ecommerce can be a big topic!