Can multiple aircraft share the same logbook?
For pilot logbooks, the requirements of "what" needs to be logged to meet training time and aeronautical experience is specified in FAR 61.51. As long as you record all of the information required by FAR 61.51 (e.g., date, total time, day/night etc.) "where" you place the information is up to you. A single conventional logbook works fine, or you can use a spreadsheet, digital device, or any type of similar recording method you choose.  Separate logbooks for each airplane is not required.

Keep in mind that you must present your logbook (in what ever form that you use to record your flight time) for inspection (upon a reasonable request from persons specified in FAR 61.51 (i)) and, if you are a student pilot on a solo cross country flight, you must carry your logbook with you (proof that you have the required instructor endorsements, etc.).

So, it's a good idea to record your flight time in a method that is easy for you to access.  For this, a conventional logbook works well.