Comparisons by the numbers
It's often very hard to understand whether a given book is really at the right level for your purposes. Terms like "Beginner" and "Intermediate" cover a huge range of reading levels, and even the ratings such as "600 Words" are often only very rough guidelines.
Rather than using only those grades, a better approach is to find a book you think is roughly at the right level, give it a try, and then try a slightly easier or tougher level as appropriate. We've included data below for the most popular series to help you make these kinds of book-to-book comparisons:
Features by Series - A list of useful features included (or not) in each series.
# of Unique Characters / Words - The simplest measure of the difficulty of a reader. This lists for each book the total number of unique characters in the story as well as the total number of unique words (e.g. 中國, the word for China, is a single word composed of two characters).
Fraction of Each HSK List Used - Useful both for assessing the difficulty of a reader (the more of the higher-level vocabulary lists used, the more difficult) and for deciding which readers would be helpful in reviewing for the different HSK exams.
Fraction of Text Covered by HSK Level - This shows the fraction of a book's text that is covered by the words included in the different HSK lists. This is probably the best measure of whether you'd be able to easily read the book (assuming for example that you knew all of the words for one of the HSK levels and no others). Knowing at least 85% of the words used is generally a good rule of thumb for being able to read for enjoyment.
(placeholder for table of series features currently at http://www.hskreaders.com/series_comparison.html) - should be modified so column titles are always visible and the reader scrolls to see the full list of rows in the table
(placeholder for # of Unique Characters / Words currently at http://www.hskreaders.com/words_counts.html) - should be modified so column titles are always visible and the reader scrolls to see the full list of rows in the table
(placeholder for Fraction of Each HSK List Used currently at http://www.hskreaders.com/107_HSK_review_table.html) - should be modified so column titles are always visible and the reader scrolls to see the full list of rows in the table
(placeholder for Fraction of Text Covered by HSK Level currently at http://www.hskreaders.com/107_bar_chart.html) - should be modified sothe chart title and color key are always visible and the reader scrolls to see the full list of entries in the chart