The best books for beginners are Genki I and Genki II, no question.

Phone apps:

  • Google Translate
  • Kanji Study
  • Tango Risto

If you can read hiragana/katakana fluently, feel free to try my Konna Kanji app as a Kanji reading quiz/practice tool that I made some time ago. JLPT N5 is your starting point.