is quietly expanding its bookstore footprint — a move that could offer clues about its ambitions for other types of stores.

The e-commerce giant told CNBC on Tuesday it will open another New York City bookstore location this summer at 7 West 34th St., across from Empire State Building.

Amazon's bookstores look ordinary at first glance. But by pulling out a mobile phone with the Amazon app, shoppers can use visual search technology to identify books and objects around them. The search reveals reviews, shipping options and price.

While Amazon is keeping the wraps on its physical grocery experiments, these high-tech brick-and-mortar bookstores could give a hint at the future of retail.

Customers walking out of an Amazon convenience store in Seattle on Tuesday haven't had to stand in any sort of line or checkout. Instead, they scan their phone when they enter, grab what they need and just walk out.

It's thanks to a technology Amazon aptly calls "just walk out," though it's currently limited to employees while it is in test mode.

The experiment is crucial for Amazon, which has invested in competing with brands like Walmart and Kroger. Data from Tabs Analytics shows that penetration of online grocery shopping has been consistently low, suggesting that people still want to go to physical stores and pick out their groceries.

If models like Amazon Go are adopted on a larger scales — perhaps also for home appliance showrooms, as suggested by The New York Times — Amazon could chart a new omnichannel experience.

— Reporting by CNBC's Deirdre Bosa. Written by Anita Balakrishnan.