Jumping in here because I totally get the laptop anxiety. I remember trying to run Stability AI Stable Diffusion XL on an aging rig and it basically turned my office into a sauna, definitely not worth the risk. If you want a middle ground, heres how I view them after using a bunch of tools over the years:

• Leonardo.ai is actually pretty solid. Its basically a friendlier interface for some SD models, so you get decent consistency without the hardware meltdowns.
• Adobe Firefly is another one to look at. Its pretty ethical and super easy to use, though it lacks some of that raw creative edge you find in the more wild models. Personally, I'd suggest grabbing a single month of whatever you pick and batching all your work in one go. Just keep your prompts consistent, maybe even try using a reference seed if the platform allows it. Saves so much time.

Honestly, skip the struggle and just grab a one-month sub to Midjourney V6 AI Image Generator. Ive been messing with this stuff since the early days and for a sci-fi novella, the coherence you get out of the box is unmatched. Youll save yourself weeks of headache trying to force local models to cooperate on a laptop that probably cant handle the compute load anyway. If you're worried about your rig, just dont bother with local installs until you have a machine with something like an NVIDIA GeForce RTX 4090 24GB GDDR6X GPU. Leonardo is decent, but for book covers, you really want that specific cinematic lighting that Midjourney nails on the first try. My advice is to sign up for the cheapest tier, spend a weekend grinding out your prompts, and cancel immediately after. Focus on using consistent style references by uploading a base image you like; that keeps the chapters from looking like a mess. You'll spend more time fighting with free tools and getting mediocre results than just paying for the sub for a month and actually finishing your project. Just make sure to save your seeds so you can iterate on the same look. You got this, three years of writing is a massive achievement.

To add to the point above: the whole landscape feels like such a mess right now. Honestly it is ridiculous how these platforms just hike prices while we are all stuck trying to make something decent without selling a kidney. Over the years I have seen so many tools promise the world only to lock the good features behind some predatory paywall that changes every other week.

• It drives me crazy how quickly they abandon support for older gear.
• Half these services feel like a total scam once you dive into the fine print.
• Quality control is basically non-existent and you end up burning hours just to get one usable result. It is just depressing that we have to jump through hoops just to get a simple cover image. The way they squeeze indie creators is just plain greedy. Good luck with the novella tho, sounds like a massive achievement getting that finished.