Wall bookshelf?

Use a stud finder to find the studs and then attach directly into the studs

You will need to use long screws to attach it to the wall studs.

There are several products for this, especially if you look into baby/child proof products. Here is a video Consumer Reports did on how to anchor furniture securely to the wall: https://www.youtube.com/watch?v=FEfqzx3Bw2k

Check this out: https://www.youtube.com/watch?v=gvviDS8mH9M

We use these from Amazon in our rental units. https://www.amazon.com/Furniture-Anti-Tilt-Bookshelf-Adjustable-Furniture/dp/B07X6CQC7V/ref=asc_df_B07X6CQC7V/?tag=hyprod-20&linkCode=df0&hvadid=385218489535&hvpos=&hvnetw=g&hvrand=16498184098357461026&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9058203&hvtargid=pla-823893324845&psc=1&tag=&ref=&adgrpid=76691052697&hvpone=&hvptwo=&hvadid=385218489535&hvpos=&hvnetw=g&hvrand=16498184098357461026&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9058203&hvtargid=pla-823893324845

If it has a solid back, you can screw directly into the studs on the wall.

Anchors into the wall

Hello securing it to the wall would be an option. Furniture-restraint device could be another to consider.

https://www.amazon.com/s?k=furniture+anti-tip+kit&gclid=Cj0KCQjwyZmEBhCpARIsALIzmnL4AJQMI0RxXeHKNSKN9oZa-51fM5O6o8pm5nyphcVE1COvaE9Esw4aAiGjEALw_wcB&hvadid=153666069109&hvdev=c&hvlocphy=9008412&hvnetw=g&hvqmt=e&hvrand=10706400165554634211&hvtargid=kwd-33223441286&hydadcr=8459_9508864&tag=googhydr-20&ref=pd_sl_18csathqne_e

Find the studs in the wall and be sure to anchor your bookcase to them

The Right Screws and Bolts

In the case of most wall cabinets, heavy-duty screws or bolts are used. One common size for mounting kitchen cabinets is a #10 by 3” screw. These are driven through the cabinet’s mounting panels and into the walls framing. A basic kitchen cabinet may use 4 of these screws to keep the dishes from crashing onto the floor. A screw like this set only in drywall is a recipe for disaster. If studs or framing are not found or available, butterfly toggles can be used. This type of anchor spreads the load over a much wider area of the drywall than the simple threads of a screw. Mounting cabinets or bookcases in concrete or on wood paneled walls may require more “specialty” types of anchors.

The Simplicity of the French Cleat

Another common mounting method for large heavy objects like cabinets and bookcases is the “French Cleat.” Here, a matched pair of beveled boards is used. One is firmly mounted to the wall, and the other is firmly mounted to the cabinet. The beauty of this mounting method is that no tools are needed once the cleats are installed. The cabinet can be removed by simply lifting it off of the wall cleat. Very large cabinets may use pairs or sets of these cleats for mounting.

Another advantage of this system is that you do not need to support the cabinet during the mounting process as with standard screw or toggle installations. The cleat is firmly mounted to the wall, via screws, toggles, bolts, etc. and then the cabinet is lifted and “hung” on the cleat. Since I do a lot of these installs solo, this is a very handy method of installation. For a French Cleat to be concealed, a bookcase or cabinet will need a recessed back panel. This allows the side panels of the cabinet to contact the wall when installed. This not only looks best but provides for more lateral stability.

Hi Shelia

Here is info for you

https://www.wikihow.com/Secure-a-Bookcase-to-a-Wall

I would highly recommend using the straps or brackets in addition to screwing it into studs. Bookshelves are notorious for falling over, especially on carpets. Kids and cats love to climb, weight isn't always distributed evenly, etc. Just make sure whatever straps, brackets you use, are also anchored in the studs.

Hi! Attaching to studs and utilizing wall anchors is the key. Not overloading shelves is important too.

You can bolt it to the wall

Make sure that you use 2.5 inch screws that are drilled into these studs behind the wall board , those studs are separated by 16 inches. That’s a national standard