13. One or more computer-readable media storing computer-executable instructions that, when executed on one or more processors, cause the one or more processors to perform acts comprising: determining a score for a word of a plurality of words of an electronic book, wherein the determining is based at least in part on: a difficulty value of the word based at least in part on a frequency of occurrence of the word in a corpus of writings; a contextual importance of the word within the electronic book; and the word having two or more meanings in a first language that are present in the electronic book; and based at least in part on the score, determining a comprehension guide to be presented with the word.
13. One or more computer-readable media storing computer-executable instructions that, when executed on one or more processors, cause the one or more processors to perform acts comprising: determining a score for a word of a plurality of words of an electronic book, wherein the determining is based at least in part on: a difficulty value of the word based at least in part on a frequency of occurrence of the word in a corpus of writings; a contextual importance of the word within the electronic book; and the word having two or more meanings in a first language that are present in the electronic book; and based at least in part on the score, determining a comprehension guide to be presented with the word. 15. One or more computer-readable media as recited in claim 13 , wherein the contextual importance of the word is based at least in part on a frequency with which the word occurs in the electronic book.