Japanese is a difficult language to many, so you have definitely come to the right place. There has been a lot of discussion online about what IMABI is and is not. However, many have extremely misunderstood the intentions here. So, I feel that it is imperative to clearly outline the ends and outs of this work.
Japanese has and will always be my passion. When I made the first page of this site in February of 2009, I didn't really know what to make. I first made basic resource pages. I initially intended to make a Kanji resource, but I quickly became absorbed with teaching grammar instead.
Later that summer I got somewhat active in helping people with simple Japanese questions on Youtube via messaging. The people I helped saw potential in me, and they encouraged me to make lessons. So, I began to periodically send them lessons. These first messages were the seeds of the site. These lessons were crammed into a small space, and they needed to be put on a website. Ever since, the site has been under construction. The site at its completion will be 300 lessons in total.
Lesson 1 has had the most editing done on it. Originally, it was about loan words particularly from English. The idea was to encourage people to learn Japanese by showing them familiar words. However, it soon became evident pronunciation should precede it. So, this was added. There is a lot about pronunciation and writing. So, Lesson 1 turned into today's 1~4. As the site came along, the advanced section was beginning, and there was still plenty of room for renovation. When I look at Lesson 1 now, I see a job well done.
One of my favorite teachers, Ms. Jones, my AP US History teacher, once wanted to look at my site as she frequently saw me working on it in class. She was bothered that I wasn't getting any money from it. She immediately knew that it was well on its way to much better things.
Most lessons have a long history. Constant edit sweeps and revisions change the appearance of them. Even for lessons that have only been around a week or so, a year from now they will have been worked on considerably.
As for the site as a whole, it would be very hard for you to find any sentence of discussion to be word for word from any other Japanese textbook or source out there.