General Motors is making it clear that it doesn't just want to be known as a carmaker.

During 2016 alone, the auto giant invested in a number of mobility services including a $500 million investment in the ride-hailing service Lyft and launched its own ride-sharing service called Maven.

The company's latest move, though, is one of its most forward-thinking endeavors.

In January, GM's Cadillac brand announced the beta launch of its new Book service, which is a subscription-based concierge service for all Cadillac cars. Users pay a flat fee and have access to whatever Cadillac car they want, whenever they want.

Because it's a beta launch, the service is only available in the New York City region, but the company has plans to expand to more US cities in the future.

We recently had the chance to try out Book for a few weeks and quickly embraced the subscription model. However, given it is still a beta version of the service, we did find a few things that could use improvement.

Here's how Cadillac's premium subscription service works and what it's like to use.