When you get about halfway through, you start to see grammar points or levels of detail that aren't commonly taught in other textbooks, not to mention more natural Japanese in the dialogues.
Japanese for Everyone is an inexpensive alternative to Genki. In fact, it covers almost as much as Genki I and II combined for only $29. Unfortunately, there's no audio component, or rather the most recent edition excludes the audio exercises featured in the original printing (though some of the audio is on YouTube).
The grammar explanations are minimal, so you'll need outside sources to supplement what you learn. When you get about halfway through, you start to see grammar points or levels of detail that aren't commonly taught in other textbooks, not to mention more natural Japanese in the dialogues.
One drawback is that kanji aren't used often in the book itself. Even in the last dialogue, it's mostly kana with some common kanji thrown in. This isn't a big issue since you're learning kanji with WaniKani, but you don't get to practice reading the kanji you do know in the otherwise excellent reading comprehension exercises.