The meanings of ‘the underlined parts’

The meanings of ‘the underlined parts’

The passage below is from The Library A Fragile History by Andrew Pettegree.

Scholars are not always the most hospitable, particularly if they are working to deadlines. Erasmus understood intimately the rhythms of the international trade, centred on the Frankfurt Fair, already in the sixteenth century the critical biannual meeting of publishers from all over Europe to exhibit their new titles and make bargains (as it still is). In the weeks before Froben’s carts set off to

Frankfurt, Erasmus was often working flat out to get a new text finished, so he much preferred to be sent books than to have their authors hanging around the house. One who despite this wormed his way into Erasmus’s good grace was the young Polish scholar Johannes àLasco (Jan Lski). The scion of a distinguished noble family, the young humanist was in the position to offer Erasmus an advantageous bargain. He would buy Erasmus’s library, but allow the great man continued use of it for the remainder of his life. It did not take Erasmus long to accept: money in hand meant a great deal to him, and à Lasco was prepared to defer the pleasure of ownership for the honour of doing Erasmus a service.

In this passage I have a few questions on the underlined parts.

First, I don’t understand ‘books’. In this sentence it says Erasmus was working to get ‘a new text’ finished. If so it should be ‘the book’ not ‘books’. (I’m not so sure on my reasoning but I’m curious.)

Second and the foremost, why ‘their authors’? In the contextual sense ‘their’ seems to refer to ‘books’ but I don’t see why. ‘Books’s author seems to be Erasmus who worked flat out to send them to Frankfurt.

Third, a related question to the second. Since 2nd question is not solved ‘have their authors hanging around the house’ is not understood. If the author of a book is Erasmus, why other authors are hanging around the house of Erasmus.

Last, on the name between parentheses. The young Polish scholar’s name is Johannes àLasco, but his another name is in the parentheses. What’s the purpose of this another name?

Thanks in advance.