Every writer has their own combination of tools they use in the process of working on their book projects. Writing software, time management, graphics programs, formatting software, etc. These are my favourite ones.

I do a lot of art. This is a free graphics program I use for most of my artwork. I do some things in Photoshop CS5 (such as painting), but the majority is done in this program.

The Guide
I use this free program to organize my series notes on my desktop. It’s not a pretty program, but it does the job.

This is my most invaluable tool for world building and organization. There are numerous paid tiers available as well as a free one. The free one has its limits and is perfectly fine. Personally, I have a paid subscription ($37.50 CAD every 3 months) and it’s worth every penny.
I also enjoy the challenges they put up on their site every so often that help with my worldbuilding.

This is a piece of formatting software I came across while looking for an alternative to the much praised Vellum. The standard edition of this program is $45 USD (I forget what the CAD cost was off-hand) and so far it’s been a great purchase.

Not the cheapest thing, but oh man, is it great! I have a monthly sub to this at the moment and it helped so much with getting my books cleaned up.

Google Drive
I can’t stress how much I love this. As much as I like working with more ‘traditional’ writing software, having all of my files in one place and 100% portable is a must for me. I’ve done all my writing on the drive for the last couple years now, and it’s increased my productivity so much.