I selected the classification 'silly' here in a good way. 'Silly' as in 'fun' because I felt it was a fun episode and a great episode for a new companion and first-time timetraveller.
The episode was not too scary for Martha, it was exciting and dangerous, thrilling perhaps, but not life-threatening in an immediate confrontational way, except for the whole end-of-humanity plot, which seemed more theoretical than actual.
I loved the one-liners, the Shakespeare and Harry Potter references, the wit and the nerve of getting someone to meet Shakespeare, flirt with him (while he seemed to flirt with the Doctor) and then tell him his breath smells.
It was definitely more fantasy than SciFi. The "power of the word" (Terry Brooks) and the "power of names" (LeGuin) has been done before, but they still managed to pull it off.