This book was in its fifth edition in 1980 (my copy), and obviously has been reprinted since then. There are more recent treatments of the subject, no doubt, and a lot of scholarship has taken place in medieval thought since that time. Nevertheless, I recommend that you buy this book (find a used copy if you can) because it is still one of the best places to get so many primary sources between the covers of one book. The introductory essays are very well done, but the value of this tome (761 pages) is the selection and depth of primary texts. This in no mere medieval cafeteria--the texts here are all selected for their importance to the overall content of each thinker's work. The selections are generous, too. With this book, you get Augustine, Boethius, Erigena, Anselm (with Gaunilo), Abelard, John of Salisbury, al-Farabi, Avicenna, al-Gazali, Averroes, Sa'adia, Solomon Ibn Gabirol, Maimonides, Bonaventure, Grosseteste, Bacon, Siger of Brabant, Aquinas (Spiritual Creatures, Summa Part I, II [first part], and the text of the 1277 condemnation), Scotus, William of Ockham, Nicholas of Autrecourt, Marsilius of Padua, and John Buridan (on Aristotle).
If you are concerned that there is no way you could get good information on so many writers in one book, let me assure you that you can. For example, you may not read all of Aquinas, but you ought to be familiar with the first part of the Summa. Similarly, you may not read all of Augustine, but some of the best of his work is here (good sections from The Teacher, Retractions, Confessions, City of God, The Trinity, and On Free Will). The important additions of Islamic and Jewish philosophy (Christian medieval thought depends upon the Aristotelian work of Muslim thinkers to a great extent) to this work make it a very nice one to have.