There’s no shortage of mothers chronicling the exploits of their children online, weighing in on parenting’s ups and downs. Emily Rapp is an expert on the latter. In Little Seal, she writes about her son Ronan, who is 2 1/2 and has Tay-Sachs disease. This isn’t your typical mommy blog. Ronan is slowly dying — he can no longer move or see, and he has had a variety of seizures — but you won’t find a more lyrical, inspiring blog. Readers can count on Rapp for a jolt of humanity and perspective amid the mundane.