I think the big difference between a junior and senior is that a junior takes tasks and gets them done, a senior knows what tasks to prioritize and estimate them.
Estimates are always garbage, but the seniors that become trusted and celebrated are the ones that can take a generic ticket and break it into tasks, rank them in priority, and estimate their weight reliably. That doesn't sound like valuable SWE skills but frankly it's way more valuable to people that are responsible for your advancement within any organization more than any concrete knowledge of software development. Don't bullshit and be right and you'll be a good senior dev.
I'd also be wary calling oneself senior with 1.5 years of experience (internships don't really count). Senior means something different everywhere, but it doesn't sound like you've had enough in the way of that.
Better than any book is mentorship. Find the nicest and best dev who can show you new things and work with them on projects that deliver value. Most of the know how in this industry (or any) isn't written down. When you plateau in growth and aren't seeing the opportunity to do more is the time to find a new organization, and 1-2 years is enough time not to look like a jerk when you do it.