Transposition Cipher

Writing the secret message in a 24 by 8 grid gives:

t t a n o p n s
h o n s t p d e
e n d o a i h e
r l t s m n e m
a i h u o g r e
b k e d m h s d
b e n d e e e t
i a d e n r l o
t t i n t s f b
h u p l t e f e
o n p y o l a a
l n e t t f l v
e e d h h b l e
w l s a i e i r
e f u t n f n y
n o d a k o g d
t r d l a r d e
s s e i b e o e
t o n c o s w p
r m l e u h n w
a e y h t e w e
i w d a s f h l
g a o d t o a l
h y w n o u t x

and then transposing (i.e. reading down the columns) gives an extract from "Alice's adventures in Wonderland" by Lewis Carroll:

therabbitholewentstraigh

tonlikeatunnelforsomeway
andthendippedsuddenlydow
nsosuddenlythatalicehadn
otamomenttothinkaboutsto
ppingherselfbeforeshefou
ndherselffallingdownwhat
seemedtobeaverydeepwellx