If you are searching for Union service records, you will probably find not much more than that single index card. Just about all the Confederate records, and those of Federal troops from southern states, as well as colored troops are pretty much complete. But the northern service records are just beginning to be entered -- it will be years before they are completed. Massachusetts is the farthest along (units of all branches numbered 1-30 so far, with a few blanks), but otherwise only scattered ones are digitized.
In the mean time, ordering the MSR and pension files (at $$$$$, and sometimes months wait), is the only real alternative.
Of course fold3 has a huge number of other types of records, among which you may well make some surprising discoveries.