I have a routing/switching background and I am interested in learning Asterisk, but am in need of a starting place. I had it installed for a while but someone hacked it and called 911, so I had the cops show up and my door (fun true story to reward you for clicking on this) after that I disconnected my home phone from it and have forgotten everything I had learned. So a book, or a good walk though, or some other resource you have found that you wish you had when first starting out.
Well after you have installed Asterisk, you should check the available applications
The book is a good reference to start but it is missing a dialplan applications index making it obsolete.
The second version had one but the third one no. So you should check the online documentation as you can see what exactly you can do.
Also if you don’t want to reinvent the wheel there are ready to go distros like Elastix, FreePBX and PIAF that are based on Asterisk and have many security measures to avoid hacking.
Well, exposing your pbx to internet traffic is always dangerous but these three distros try to avoid hacking. You should check them.