Coming soon and available for pre-order is my new book - "Arduino Workshop" from No Starch Press.
Over 60 projects that will take the absolute beginner from blinking an LED through to the most complex of topics 
For more information please visit - Arduino Workshop, 2nd Edition | No Starch Press
I have put a link to your tutorial site on the bottom of my replies because, I have found your site very helpful. I hope you do well with your book, I may buy one when I am able. Thank you for your efforts!
The tronixstuff tutorials are very good and I used them myself when starting out, but they could really do with being updated for the latest IDEs. There have been a number of occasions recently where being able to point someone at the GSM tutorial would have been ideal, but I couldn't without having to deal with the IDE issue.
Having said that, I also hope the book does well for you.
@John, Good luck with your book and thanks for your web tutorials, I've found them very useful
I too have a link to your site in my footer..
love it!
good luck on sales!
Thank you everyone for your kind words and comments.
With regards to the website, it isn't my day job so sometimes it's difficult to spend the time required to update it. I'm renewing and updating the tutorials as time allows, we're about one quarter of the way through it.
The GSM one will be changed a fair bit, might be looking at a different shield. Time will tell.
cheers
John