Read the file by below way:
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *bookDirectoryPath = [documentsDirectory stringByAppendingPathComponent:@"book"];
NSArray *fileNamesArray = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:bookDirectoryPath error:nil];
for(NSString *fileName in fileNamesArray)
{
if([[fileName pathExtension] isEqualToString:@"html"])
{
NSError *err = nil;
NSString *fileNamePath = [bookDirectoryPath stringByAppendingPathComponent:fileName];
NSString *htmlContent = [NSString stringWithContentsOfFile:fileNamePath
encoding:NSUTF8StringEncoding
error:&err];
NSLog(@"%@",htmlContent);
}
}