How should I start learning about SAP?

You should join https://open.sap.com.

That is basically a free learning portal recently made by SAP.

"Imagine you could go back to university to learn more about topics that are key to success in the SAP ecosystem, and combine your studies with your busy work schedule.

Well, now you can: With openSAP.

The first openSAP course has now started, and more will be coming soon.

For a complete overview about the SAP Education offerings please refer to the SAP Training and Certification Shop." SAP Open

First, SAP is so vast you will never be able to know every part of it. There are so many functionnal subjects and technologies that this is mind-numbing.

Courses can be used either for a first introduction (but this is costly for such a use) or for extremely advanced subject (better).

SAP is a full environment. The code for most of the content is available. Thus, checking how SAP has done something can/may/will help you understand the technology or the subject. (Btw, a lot of comments are in German...) in-system transaction se80 is particularly useful in this aspect, as it show all related data to a program.

Also, SDN is your friend. forum, how-to, white papers are present... it will help you. A few in-system transactions (se83) are to be used as example for coding technics.

SAP is a beast to wrangle down .. some suggestions:

• For a programmer: Get a decent ABAP programming book. Most concepts will be pretty familiar, and they give you a good starting point to better understand the system.
• For a "business user": Other than going to an expensive course (mostly wasted time/money in my opinion), sit down with a user and have him/her explain too you what they are doing for an hour or two.
• For a "customizer": This is where things get really difficult as there are a gazillion of steps and choices and places to change things. Having someone more experienced helps. As you noted, books/articles are mostly not very helpful as they are usually at a loss to explain concepts.

A couple of things to keep in mind as well:

• SAP is "so big" that it is impossible to "know it all".
• SAP is written by some smart and some not so smart people. Your inability to "grok" things may be caused by some really bad programmer building a bunch of stupid solutions to problems he hasn't understood.
• SAP is notorious for coming up with their own language or by repurposing buzzwords and adding their own special meaning. This adds to the magic and confusion.

Just get started, ask questions, try out some things, don't be afraid by the size of it. Pretty soon you'll get better at it ...