Put down that novel and get to work. Continental and United airlines each recently announced plans to offer in-flight e-mail service. Continental was the first out of the block, launching the $15.98-per-flight service this summer on its Boeing 757 fleet, with plans to expand to smaller jets through the fall. United expects to get passengers connected by the end of the year and to charge a similar fee. Both airlines are using Verizon's JetConnect service, which includes e-mail, instant messaging, and other information services, but not full Internet access.