"Humulin N" is a brand name for NPH, a kind of insulin that has a delayed response by having zinc added. NPH can work pretty good as a basal insulin - I did this for a couple of decades.
"Humulin R" is a brand name for good old "Regular insulin".
All the major insulin selling companies have their own brand names for NPH and Regular. Don't get too much wrapped up in the brand names, it's about the same no matter who sells it. They are very old-school types and have been fairly standard for the past 60 years. About 20 years ago most of the production shifted from insulin made from pork and beef (animal) pancreases, to genetically engineered human insulin, and this is where the "Humil" (e.g. Human) part of the "Humulin" name comes from.
I found it worked pretty well, with 4 small shots a day. e.g. for most of the 20 years I did MDI with NPH as my basal, I took 5 units every 6 hours, 4 times a day.
NPH is not at all a "flat" insulin, it has a really broad long peak about 3-8 hours after injection.
Curves of various types of insulin found at http://www.endotext.org/diabetes/diabetes20/ch01s06.html
And remember those curves are idealized curves. For example they show "glargine" (e.g. Lantus or Levemir) as ramping up and then being perfectly flat out to 24 hours. It is not at all perfectly flat out to 24 hours!!!
By stacking small doses of NPH every 6 hours, the overall effect is quite flat. In some sense I feel that 4xNPH for basal, has superior flatness to 1xLantus every day. Right now I do Lantus twice a day (12 hours apart) and that's not bad but sometimes I feel 4xNPH was superior.
A very old fashioned (e.g. before MDI) way of using NPH, was by taking a shot of NPH+regular in the morning. The regular peaked an hour or two after the shot (sort of like a bolus to cover breakfast), the NPH peaked 5 hours after (sort of like a bolus to cover lunch), and the overlap of the activity curves between the broad peaks kind of worked like a basal. The peaks were not very sharp and the basal not very flat. And then in the evening before supper there was another NPH+regular shot, the regular to cover supper and the NPH as sort of a basal. Because of the broadness of the peaks snacks were often necessary in between meals to keep bg up, and "eating to the insulin" could cause weight gain. This wasn't the worst regime in the world but I did a lot better after I switched to more of a MDI type regime (using the same R+N but more shots) in the mid 80's.