I am not referring to old books but any book that has been written in the last century. Every time I try to understand Shia beliefs from Hadiths I get faced by their claims that not all their Hadiths are authentic. Has anybody ever collected the authentic ones and put them in one book?
First let me address your concern about claims that Shia hadith books are not reliable. Quiet conversely, Shia hadiths are generally more reliable for some reasons among which are these two:
Shia believes in the Isma of their twelve Imams (a.s), and have received the authentic hadiths of the Prophet of Islam (PBUH) from the Imams for more than 250 years after the Prophet of Islam passed away. Note that this period (the first 100 years after the death of the Prophet of Islam) was exactly a time that most of the falsifications in hadiths occurred, because of the political issues, and also the prohibition of writing hadiths during Umar(a.s) period.
Generally, Shia more than all other branches of Islam emphasizes on reason and philosophy. This is why most of the Muslim philosophers were Shia.
Now, there are four well-known books of Shia hadith that you may know them :
Among these probably the most important, and also reliable is the first one, al-Kafi. This is an old book and is written a few decades after the last Shia Imam, so the falsifications at the time of writing the book were minimal. But, in recent decades, there are some efforts to analyze this book trying to separate historically weaker ones. One of the outcomes is the book Sahih al-Kafi (meaning the correct of al-Kafi). This book has collected the most reliable hadiths of the original al-Kafi.
To the best of my knowledge, collecting and presenting of such thing as you said could be considered as a based-opinion. But in order to help you to reach your goal, I strongly suggest you to refer to the following books which could be considered as the four more authentic books of Shiite. Therefore, there are four well-known books of Shiite hadith that you can see them as following:
Kitab al-Kafi / الكافي، محمد بن یعقوب الكليني (متوفى 329هـ)؛
Man la yahduruhu al-Faqih / مَن لا یَحضُرُهُ الفَقِیه، تألیف محمدبن على بن بابویه، معروف به شیخ صدوق (متوفى 381هـ)؛
Tahdhib al-Ahkam / تهذیب الاحكام ، محمد بن حسن الطوسي، معروف به شیخ الطائفه (متوفى 460هـ).
Al-Istibsar / الاستبصار فِیمَا اختُلف مِن الاخبار ، تألیف شیخ الطائفه
Actually, you can consider the books which have inferred from those four books as authentic books even if they have been written in the last century. (As their sources).
hi i recommend you to find Al Ghadir book https://en.wikipedia.org/wiki/Al-Ghadir
Al Ghadir (Arabic: الغدير في الكتاب والسنة والأدب) (that is "The Ghadir in the Book, the Sunnah, and Literature") is a 20-volume book written by the Iranian Shia scholar Abd Al Husayn Amini.