If that e-book does not involve any illegal stuff you can use the forum's ad space which was posted the link above.
Besides for a-ads which were mentioned above you can try Godzilla as well. Also, how about coinad? Though I never tried them yet but base on some google reviews this sites are the best for the ad industry related to crypto.
I invested in coinzilla 300$
150$ for brand awareness traffic -> No sells, the traffic is mainly from faucets websites, I had over 250 clicks but they are not interested in the page, average visit duration was 5 seconds... so, this is shady, but works only for brand awareness.
150$ for premium traffic -> 1 sell, the traffic is provided from ads on bigger websites, but the CPM is so expensive, I got ±20 click for 150$.
Aads are kind of the same, I will look over coinad and that all networks that was posted in this topic.
Now I'm searching a way to get affiliates, I have a full platform with stats, resources and the commission is 25%