Yes,you are liable to register under gst as you have crossed the threshold limit of Rs. 40 Lakh(in case of goods and Rs.20lacs in case of services.) If you are a inter state supplier then there is no threshold limit,registration is compulsory.
If you are dealing only in books such as text books or books for the disabled (which are exempt). Then registration is not required. Stationery item is not exempt.