I would say that a very high portion of users here have never used blender before 2.50, the people that did use 2.49 or earlier back in the day would most likely not have used the older version in several years (2.50 was released in July 2010 - 6 years ago) so you will most likely not get very much help with questions specific to the older versions. This is especially relevant with anything python related, python in 2.49 and 2.50 is extremely different and the use of python has increased substantially since 2.50 so I wouldn't expect you to get any useful response to a 2.49 python question.
That means the book you have will be your biggest source of help.
Having said that, I will say that most of what you do learn can be used in a new version of blender. There have been a lot of new additions but apart from the cosmetic makeover which means you will need to find the new location of things, what you learn can still be used in 2.77.
I would suggest you go over a quick introduction to a newer version like CGCookies blender basics and then try doing the tasks in the book using the new version. If you come here and say "I am following an old tutorial and I can't find the subdivide multi option" then someone will tell you how to find it.
If that example got you curious, in 2.49 the specials W menu had subdivide, subdivide multi, subdivide multi fractal and subdivide smooth. In 2.77 we only have subdivide and subdivide smooth (both of which are the same operator with different options), but we can adjust the options used to get the same functionality as 2.49. Either at the bottom of the toolshelf region or the floating panel by pressing F6.
And that is one of the changes you will notice, some actions in 2.49 would bring up a dialog for you to adjust the values to be used. Now default options are used and you can choose to adjust them if you wish. Where in 2.49 we had to undo and redo entering different values, now we just adjust the values after and the changes happen dynamically.