I have Tobira but am not using it at the moment cause I am travelling :D. For me it is a decent textbook. Since my aim was going for N3 in July, I supplemented with Kansen Masters and eventually dropped Tobira completely. Not because I didn’t like it but more because of time constraints.
I feel like Tobiras texts are masterfully crafted, don’t make you bored, and use a lot of grammar from previous chapters. It also has a decent amount of really useful vocabulary you can learn from it. If you use their online resources you can even get some okayisch listening out of it. I don’t feel it is the best book for grammar though, especially if you don’t buy the grammar excercise book alongside it. The difficulty and usefullness of the Grammar points (at least in the earlier chapters i did) varies greatly.
That being said if you have specific things you want to work on it might be better to just get a Sou-matome or a Kansen master. These books are VERY dense and honestly sometimes bore me to death. But I think they are an excellent preparation for JLPT!
Whatever I do, I like to be able to look up at least two different grammar explanations. So I plan to slowly work through Tobira and do masters when i’m trying to supplement for a specific aim I have (JLPT, better listening etc).
It worked great for N3 for me so I plan to stick with it even if some of the grammar in Tobira is only review and pretty easy.
Like all the others have said. Find your own preffred way to use the materials you have. If you are pressed for money and wanna advance fast for a JLPT I would recommend different books from Tobira though!
Also take a look at the TRY! series of books if you are really scraping for money. They offer a great overview over what you need to pass each JLPT level for a pretty cheap price.