I would definitely recommend Joel Spolsky's Smart and Gets Things Done. It's quite readable in one weekend since it's nice and small, and to the point with most chapters.
At the early stage of a startup, you're going to need folks who can wear multiple hats, so for example in one software company where I was their 4th employee, hired as a software developer, I also had to take lead when it came to things I knew well, like technical operations (setting up VoIP, servers, source control in the new office) as well as things I learnt on the job from the founders like recruiting, technical interviewing, behavioral interviewing, event management, negotiating terms and conditions, office management etc.
I vouch for Joel's book because it reinforces the real lessons I learnt on the field about the value of having persons like me who can 'run with' tasks when given them, even if it's outside their expertise, and don't need much hand holding to get the job done.
Having the book also enabled me to transfer some of this knowledge in a more concrete way (what's more concrete than a book) to those who I handed over some of my 'hats' to as the company grew.
For hiring, the 3 stages in the previous answer are excellent guidelines, that is of
English language capabilities, both reading and writing. It's especially important to gauge their attention to detail here, since English can be a pretty complex language even for those of us who are native speakers. Do they speak and write in a clear and concise way that you can easily get the essentials of whatever message they are attempting to convey? Do they 'connect the dots' when speaking about ideas, and do they speak with confidence? (Confidence is very essential for client-facing roles)
Technical assessment, by the current team of technical persons they're expected to work with. You want the team to gel quickly and reach productivity 'as soon as'. Having them be part of the interviewing process allows the team-building to get an early start, since if the interviewee is hired, they're expecting it, they've participated in the process, and they're on board with believing they can work with this person, so the new employee's "Day One" becomes more of a "Two Weeks Into The Job" in terms of team-building timelines and team productivity.
If you're looking for your technical lead and you're not a technical person, this can be a challenge since you have no baseline to evaluate their technical expertise other than what they've stated on their resume, so you're probably rely more on the behavioral assessment and their ability to be 'smart and get things done' which they can show by referencing examples from their past job roles. That way, even if they're not the technical cream of the crop, or even at the technical leadership level, their 'smart and get things done' mentality will get them there with minimal overhead and hand holding from your founders.
Behavioral assessment, since as a new company you're creating a specific work culture that in your founders' minds is seen as critical to the success of the company, and you want to make sure your early employees can champion that culture and encourage others who join later to be just as enthusiastic about what makes working with your company great.