After memorizing the Holy Quran, what are the recommended books for seeking knowledge? Are there books about the righteous and the Tabi'een (the generation that followed the Companions) who possessed high resolve and determination, which could motivate the reader to strive and be influenced?

As for seeking knowledge: Look for scholars in your place of residence and adhere to them. If that is not possible, then start with easy and accessible books in every field, such as: Aqīdat al-Mu'min (The Creed of the Believer) by Al-Jaza'iri in creed, Al-Fiqh al-Muyassar (Simplified Fiqh) in jurisprudence, Al-Mukhtasar fi al-Tafsir (The Concise Interpretation) in Tafsir, and Sharh al-Arba'in al-Nawawiyyah (Explanation of the Forty Nawawi Hadiths) by Ibn Uthaymeen in Hadith. Then, gradually progress. You can also benefit from the audio library of Shaykh Ibn Uthaymeen.

As for books that narrate the stories of the righteous in their diligence in seeking knowledge, examples include: Siyar A'lam al-Nubala' (Biographies of Noble Figures) by Al-Dhahabi, and Sifat al-Safwah (The Qualities of the Elite) by Ibn al-Jawzi.